src/sage/modules/vector_space_morphism.py: Remove use of is_VectorSpace

src/sage/modules/vector_space_morphism.py

@@ -696,7 +696,7 @@ def linear_transformation(arg0, arg1=None, arg2=None, side='left'):
     from sage.categories.homset import Hom
     from sage.matrix.constructor import matrix
     from sage.modules.free_module import VectorSpace
-    from sage.modules.module import is_VectorSpace
+    from sage.modules.module import Module
     try:
         from sage.modules.vector_callable_symbolic_dense import (
             Vector_callable_symbolic_dense,
@@ -706,8 +706,6 @@ def linear_transformation(arg0, arg1=None, arg2=None, side='left'):
 
     if side not in ['left', 'right']:
         raise ValueError("side must be 'left' or 'right', not {}".format(side))
-    if not (is_Matrix(arg0) or is_VectorSpace(arg0)):
-        raise TypeError('first argument must be a matrix or a vector space, not {}'.format(arg0))
     if is_Matrix(arg0):
         R = arg0.base_ring()
         if not R.is_field():
@@ -722,14 +720,15 @@ def linear_transformation(arg0, arg1=None, arg2=None, side='left'):
         arg2 = arg0
         arg0 = VectorSpace(R, arg2.nrows())
         arg1 = VectorSpace(R, arg2.ncols())
-    elif is_VectorSpace(arg0):
-        if not is_VectorSpace(arg1):
+    elif isinstance(arg0, Module) and arg0.base_ring().is_field():
+        if not (isinstance(arg1, Module) and arg1.base_ring().is_field()):
             msg = 'if first argument is a vector space, then second argument must be a vector space, not {0}'
             raise TypeError(msg.format(arg1))
         if arg0.base_ring() != arg1.base_ring():
             msg = 'vector spaces must have the same field of scalars, not {0} and {1}'
             raise TypeError(msg.format(arg0.base_ring(), arg1.base_ring()))
-
+    else:
+        raise TypeError('first argument must be a matrix or a vector space, not {}'.format(arg0))
     # Now arg0 = domain D, arg1 = codomain C, and
     #   both are vector spaces with common field of scalars
     #   use these to make a VectorSpaceHomSpace