code: def validate_is_non_abstract_edge_type(self, edge_classname):
          
          element = self.get_edge_schema_element_or_raise(edge_classname)
  
          if element.abstract:
              raise InvalidClassError(u'Expected a non-abstract vertex class, but {} is abstract'
                                      .format(edge_classname))
docs: Validate that a edge classname corresponds to a non-abstract edge class.