docs: def _change_schema(self, schema, action, name=None, func=None):
          """Internal method to change a schema.
          """
          if self.oport.schema.schema() == schema.schema():
              return self
  
          if func is None:
              func = streamsx.topology.functions.identity
  
          _name = name
          if _name is None:
              _name = action 
          css = self._map(func, schema, name=_name)
          if self._placeable:
              self._colocate(css, action)
          return css