[Enh] Specialize runtime for SPM

Author: balbasty

spm/__init__.py

@@ -1,12 +1,12 @@
 from mpython import (
-    Runtime,
     MatlabClass,
     MatlabFunction,
     Cell,
     Struct,
     Array,
     SparseArray,
 )
+from ._runtime import Runtime
 from ._version import __version__
 from .file_array import file_array
 from .gifti import gifti

spm/_runtime.py

@@ -0,0 +1,23 @@
+from mpython.runtime import Runtime as RuntimeBase
+
+
+class Runtime(RuntimeBase):
+    """
+    Runtime specialization that imports the correct CTF.
+    """
+
+    @classmethod
+    def _import_runtime(cls):
+        import spm_runtime
+        return spm_runtime
+
+
+class RuntimeMixin:
+    """
+    Mixin that SPM classes must inherit so that they can call the
+    correct runtime.
+    """
+
+    @classmethod
+    def _runtime(cls):
+        return Runtime