sage.plot: Remove use of is_CallableSymbolicExpression, is_SymbolicEq…

…uation

src/sage/plot/contour_plot.py

@@ -1195,8 +1195,8 @@ def f(x,y):
         ...
         ValueError: only one of color or rgbcolor should be specified
     """
-    from sage.symbolic.expression import is_SymbolicEquation
-    if is_SymbolicEquation(f):
+    from sage.structure.element import Expression
+    if isinstance(f, Expression) and f.is_relational():
         if f.operator() != operator.eq:
             raise ValueError("input to implicit plot must be function "
                              "or equation")

src/sage/plot/misc.py

@@ -15,7 +15,7 @@
 
 from sage.ext.fast_eval import fast_float
 
-from sage.structure.element import is_Vector
+from sage.structure.element import is_Vector, Expression
 
 def setup_for_eval_on_grid(funcs, ranges, plot_points=None, return_vars=False):
     """
@@ -187,15 +187,13 @@ def unify_arguments(funcs):
         sage: sage.plot.misc.unify_arguments((x+y,x-y))
         ((x, y), (x, y))
     """
-    from sage.symbolic.callable import is_CallableSymbolicExpression
-
     vars=set()
     free_variables=set()
     if not isinstance(funcs, (list, tuple)):
         funcs = [funcs]
 
     for f in funcs:
-        if is_CallableSymbolicExpression(f):
+        if isinstance(f, Expression) and f.is_callable():
             f_args = set(f.arguments())
             vars.update(f_args)
         else:

src/sage/plot/plot3d/plot3d.py

@@ -1046,13 +1046,13 @@ def plot3d(f, urange, vrange, adaptive=False, transformation=None, **kwds):
         Graphics3d Object
     """
     if transformation is not None:
-        params=None
-        from sage.symbolic.callable import is_CallableSymbolicExpression
+        params = None
+        from sage.structure.element import Expression
         # First, determine the parameters for f (from the first item of urange
         # and vrange, preferably).
         if len(urange) == 3 and len(vrange) == 3:
             params = (urange[0], vrange[0])
-        elif is_CallableSymbolicExpression(f):
+        elif isinstance(f, Expression) and f.is_callable():
             params = f.variables()
 
         from sage.modules.vector_callable_symbolic_dense import Vector_callable_symbolic_dense