sagemathgh-41459: Fix docstring formatting to raw string literals
    
<!-- ^ Please provide a concise and informative title. -->
<!-- ^ Don't put issue numbers in the title, do this in the PR
description below. -->
<!-- ^ For example, instead of "Fixes sagemath#12345" use "Introduce new method
to calculate 1 + 2". -->
<!-- v Describe your changes below in detail. -->
<!-- v Why is this change required? What problem does it solve? -->
<!-- v If this PR resolves an open issue, please link to it here. For
example, "Fixes sagemath#12345". -->

Fix a few missing `r-strings` for docs, found by running pytest and
those changes here are extracted from sagemath#36981.

Also includes a few other minor linter fixes in the touched files.

### 📝 Checklist

<!-- Put an `x` in all the boxes that apply. -->

- [ ] The title is concise and informative.
- [ ] The description explains in detail what this PR is about.
- [ ] I have linked a relevant issue or discussion.
- [ ] I have created tests covering the changes.
- [ ] I have updated the documentation and checked the documentation
preview.

### ⌛ Dependencies

<!-- List all open PRs that this PR logically depends on. For example,
-->
<!-- - sagemath#12345: short description why this is a dependency -->
<!-- - sagemath#34567: ... -->
    
URL: sagemath#41459
Reported by: Tobias Diez
Reviewer(s): Frédéric Chapoton

Author: Release Manager

src/sage/graphs/dot2tex_utils.py

@@ -9,8 +9,9 @@
 # ****************************************************************************
 
 import re
-from sage.misc.latex import latex
+
 from sage.misc.cachefunc import cached_function
+from sage.misc.latex import latex
 
 
 @cached_function
@@ -68,7 +69,7 @@ def assert_have_dot2tex():
 
 
 def quoted_latex(x):
-    """
+    r"""
     Strips the latex representation of ``x`` to make it suitable for a
     ``dot2tex`` string.
 

src/sage/graphs/graph_list.py

@@ -168,7 +168,7 @@ def from_graph6(data, immutable=False):
 
 
 def from_sparse6(data, immutable=False):
-    """
+    r"""
     Return a list of Sage Graphs, given a list of sparse6 data.
 
     INPUT:

src/sage/groups/matrix_gps/named_group.py

@@ -256,7 +256,7 @@ def _repr_(self):
         return self._name_string
 
     def _latex_(self):
-        """
+        r"""
         Return a LaTeX representation.
 
         OUTPUT: string

src/sage/homology/chain_complex.py

@@ -49,23 +49,22 @@
 from copy import copy
 from functools import reduce
 
-from sage.structure.parent import Parent
-from sage.structure.element import ModuleElement, Vector, coercion_model
+from sage.homology.homology_group import HomologyGroup
+from sage.matrix.constructor import matrix
+from sage.matrix.matrix0 import Matrix
 from sage.misc.cachefunc import cached_method
-
-from sage.rings.integer_ring import ZZ
+from sage.misc.latex import latex
+from sage.misc.persist import register_unpickle_override
 from sage.modules.free_module import FreeModule
 from sage.modules.free_module_element import vector
-from sage.matrix.matrix0 import Matrix
-from sage.matrix.constructor import matrix
-from sage.misc.latex import latex
 from sage.rings.fast_arith import prime_range
-from sage.homology.homology_group import HomologyGroup
-from sage.misc.persist import register_unpickle_override
+from sage.rings.integer_ring import ZZ
+from sage.structure.element import ModuleElement, Vector, coercion_model
+from sage.structure.parent import Parent
 
 
 def _latex_module(R, m):
-    """
+    r"""
     LaTeX string representing a free module over ``R`` of rank ``m``.
 
     INPUT:
@@ -1321,35 +1320,34 @@ def change_ring(X):
                           for order, gen in zip(orders, gens)]
             else:
                 answer = []
-        else:
-            if base_ring.is_field():
-                d_in_rank = self.rank(deg-differential, ring=base_ring)
-                answer = HomologyGroup(d_out_nullity - d_in_rank, base_ring)
-            elif base_ring == ZZ:
-                if d_in.ncols() == 0:
-                    all_divs = [0] * d_out_nullity
-                else:
-                    if algorithm in ['auto', 'no_chomp']:
-                        if ((d_in.ncols() > 300 and d_in.nrows() > 300)
-                            or (min(d_in.ncols(), d_in.nrows()) > 100 and
-                                d_in.ncols() + d_in.nrows() > 600)):
-                            algorithm = 'dhsw'
-                        else:
-                            algorithm = 'pari'
-                    if algorithm == 'dhsw':
-                        from sage.homology.matrix_utils import dhsw_snf
-                        all_divs = dhsw_snf(d_in, verbose=verbose)
-                    elif algorithm == 'pari':
-                        all_divs = d_in.elementary_divisors(algorithm)
-                    else:
-                        raise ValueError('unsupported algorithm')
-                all_divs = all_divs[:d_out_nullity]
-                # divisors equal to 1 produce trivial
-                # summands, so filter them out
-                divisors = [x for x in all_divs if x != 1]
-                answer = HomologyGroup(len(divisors), base_ring, divisors)
+        elif base_ring.is_field():
+            d_in_rank = self.rank(deg-differential, ring=base_ring)
+            answer = HomologyGroup(d_out_nullity - d_in_rank, base_ring)
+        elif base_ring == ZZ:
+            if d_in.ncols() == 0:
+                all_divs = [0] * d_out_nullity
             else:
-                raise NotImplementedError('only base rings ZZ and fields are supported')
+                if algorithm in ['auto', 'no_chomp']:
+                    if ((d_in.ncols() > 300 and d_in.nrows() > 300)
+                        or (min(d_in.ncols(), d_in.nrows()) > 100 and
+                            d_in.ncols() + d_in.nrows() > 600)):
+                        algorithm = 'dhsw'
+                    else:
+                        algorithm = 'pari'
+                if algorithm == 'dhsw':
+                    from sage.homology.matrix_utils import dhsw_snf
+                    all_divs = dhsw_snf(d_in, verbose=verbose)
+                elif algorithm == 'pari':
+                    all_divs = d_in.elementary_divisors(algorithm)
+                else:
+                    raise ValueError('unsupported algorithm')
+            all_divs = all_divs[:d_out_nullity]
+            # divisors equal to 1 produce trivial
+            # summands, so filter them out
+            divisors = [x for x in all_divs if x != 1]
+            answer = HomologyGroup(len(divisors), base_ring, divisors)
+        else:
+            raise NotImplementedError('only base rings ZZ and fields are supported')
         return answer
 
     def _homology_generators_snf(self, d_in, d_out, d_out_rank):
@@ -1769,7 +1767,7 @@ def module_art(n):
         return concatenated
 
     def _latex_(self):
-        """
+        r"""
         LaTeX print representation.
 
         EXAMPLES::

src/sage/interfaces/expect.py

@@ -55,6 +55,7 @@
 import sage.interfaces.abc
 from sage.cpython.string import bytes_to_str, str_to_bytes
 from sage.env import LOCAL_IDENTIFIER, SAGE_EXTCODE
+from sage.interfaces import quit
 from sage.interfaces.interface import (
     Interface,
     InterfaceElement,
@@ -65,8 +66,6 @@
 from sage.misc.object_multiplexer import Multiplex
 from sage.structure.element import RingElement
 
-from . import quit
-
 BAD_SESSION = -2
 
 # The subprocess is a shared resource.  In a multi-threaded
@@ -693,7 +692,7 @@ def detach(self):
         self._reset_expect()
 
     def _quit_string(self):
-        """
+        r"""
         Return the string which will be used to quit the application.
 
         EXAMPLES::

src/sage/interfaces/gp.py

@@ -149,7 +149,12 @@
 
 lazy_import('sage.rings.cc', 'CC')
 
-from .expect import Expect, ExpectElement, ExpectFunction, FunctionElement
+from sage.interfaces.expect import (
+    Expect,
+    ExpectElement,
+    ExpectFunction,
+    FunctionElement,
+)
 
 
 class Gp(ExtraTabCompletion, Expect):
@@ -308,7 +313,7 @@ def _function_class(self):
         return GpFunction
 
     def _quit_string(self):
-        """
+        r"""
         Return the string used to quit the GP interpreter.
 
         EXAMPLES::

src/sage/interfaces/interface.py

@@ -831,7 +831,7 @@ def __reduce__(self):
         return self.parent(), (self._reduce(),)
 
     def _reduce(self):
-        """
+        r"""
         Helper for pickling.
 
         By default, if ``self`` is a string, then the representation of