Tests for simplifications + postprocessing + small fixes

postprocessing.py

@@ -4,7 +4,7 @@ import numpy as np
 def vector_field_interpolator(vector_field):
     from scipy.interpolate import RegularGridInterpolator
     coordinates = [np.arange(s) + 0.5 for s in vector_field.shape[:-1]]
-    return RegularGridInterpolator(*coordinates, vector_field)
+    return RegularGridInterpolator(coordinates, values=vector_field)
 
 
 def scalar_field_interpolator(scalar_field):

simplificationfactory.py

@@ -16,8 +16,7 @@ def create_simplification_strategy(lb_method, cse_pdfs=False, cse_global=False,
 
     s = SimplificationStrategy()
 
-    expand = partial(apply_to_all_assignments, operation=sp.expand)
-    expand.__name__ = "expand"
+    expand = apply_to_all_assignments(sp.expand)
 
     if isinstance(lb_method, MomentBasedLbMethod):
         s.add(expand)