code: def _conflicting_defaults(typename, conflicts):
      
      message = "\nclass {C} received conflicting default implementations:".format(
          C=typename,
      )
      for attrname, interfaces in conflicts.items():
          message += dedent(
              """
  
              The following interfaces provided default implementations for {attr!r}:
              {interfaces}"""
          ).format(
              attr=attrname,
              interfaces=bulleted_list(sorted(map(getname, interfaces))),
          )
      return InvalidImplementation(message)
docs: Format an error message for conflicting default implementations.
  
      Parameters
      ----------
      typename : str
          Name of the type for which we're producing an error.
      conflicts : dict[str -> list[Interface]]
          Map from strings to interfaces providing a default with that name.
  
      Returns
      -------
      message : str
          User-facing error message.