PR template and bugfix

Author: mimakaev

.github/pull_request_template.md

@@ -5,6 +5,5 @@ _Describe what this PR is for_
 
 ## PR Checklist
 
-- [] apply "black" to the whole codebase (`black .`) 
-- [] apply isort to the codebase (`isort .`)
-- [] fun `flake8` and try to resolve all the issues (work in progress!)
+- [] apply `black` and `isort` to the whole codebase (`black .; isort .`) 
+- [] Make sure that `flake8` does not raise any warnings

polychrom/forces.py

@@ -722,7 +722,7 @@ def heteropolymer_SSW(
 def cylindrical_confinement(
     sim_object,
     r,
-    bottom: int | Literal[True, None, False] = None,
+    bottom: int | Literal[True, None] = None,
     k=0.1,
     top=9999,
     name="cylindrical_confinement",
@@ -731,7 +731,7 @@ def cylindrical_confinement(
 
     bottom = 0 if bottom is True else bottom
 
-    if bottom:
+    if bottom is not None:
         force = openmm.CustomExternalForce(
             "kt * k * ("
             " step(dr) * (sqrt(dr*dr + t*t) - t)"