[python][assembly] Improve style, add some, use wrapper helpers

python/dumux/assembly/__init__.py

+"""Classes and function related to the assembly of linear systems"""
+
 from dune.generator.generator import SimpleGenerator
 from dune.common.hashit import hashIt
+from dumux.wrapping import cppWrapperCreator, cppWrapperClassAlias
+
+
+@cppWrapperCreator
+def _createFVAssembler(*, problem, gridVariables, model, diffMethod="numeric", isImplicit=True):
+    """
+    Create an FVAssembler object
 
+    Args:
+        problem: A problem instance (boundary & initial conditions)
+        gridVariables: A grid variable instance (primary & secondary variables defined on a grid)
+        model: A DuMux model configuration instance
+        diffMethod (str): The method to compute derivatives of the residual (numeric or analytic)
+        isImplicit (bool): If the time discretization method is implicit or explicit
 
-def FVAssembler(*, problem, gridVariables, model, diffMethod="numeric", isImplicit=True):
+    Returns:
+        An assembler object (Python-bindings of the corresponding C++ type)
 
-    TypeTag = model.getTypeTag()
+    Usage:
+        assembler = FVAssembler(
+            problem=problem, gridVariables=gridVars, model=model, diffMethod=diffMethod
+        )
+    """
 
     if diffMethod == "numeric":
-        dm = "Dumux::DiffMethod::numeric"
+        cppDiffMethod = "Dumux::DiffMethod::numeric"
     elif diffMethod == "analytic":
-        dm = "Dumux::DiffMethod::analytic"
+        cppDiffMethod = "Dumux::DiffMethod::analytic"
     else:
         raise ValueError(f"Unknown diffMethod {diffMethod}")
 
-    assemblerType = f"Dumux::FVAssembler<{TypeTag}, {dm}, {int(isImplicit)}>"
+    assemblerType = f"Dumux::FVAssembler<{model.cppType}, {cppDiffMethod}, {int(isImplicit)}>"
     includes = (
         problem._includes + problem.gridGeometry()._includes + ["dumux/assembly/fvassembler.hh"]
     )
@@ -26,6 +46,11 @@ def FVAssembler(*, problem, gridVariables, model, diffMethod="numeric", isImplic
         assemblerType,
         moduleName,
         holder="std::shared_ptr",
-        preamble=model.getProperties(),
+        preamble=model.cppHeader,
     )
     return module.FVAssembler(problem, problem.gridGeometry(), gridVariables)
+
+
+@cppWrapperClassAlias(creator=_createFVAssembler)
+class FVAssembler:
+    """Class alias used to instantiate an FVAssembler"""