Add 'implementation' keyword to self.implementations (if exists)

Author: Newtech66

src/sage/categories/pushout.py

@@ -3296,6 +3296,7 @@ def __init__(self, polys, names, embeddings=None, structures=None,
         self.latex_names = latex_names
         kwds_self = dict(kwds.items())
         if 'implementation' in kwds_self:
+            self.implementations[0] = kwds_self['implementation']
             del kwds_self['implementation']
         self.kwds = kwds_self