code: def _coltype_to_typeengine(coltype: Union[TypeEngine,
                                            VisitableType]) -> TypeEngine:
      
      if isinstance(coltype, VisitableType):
          coltype = coltype()
      assert isinstance(coltype, TypeEngine)
      return coltype
docs: An example is simplest: if you pass in ``Integer()`` (an instance of
      :class:`TypeEngine`), you'll get ``Integer()`` back. If you pass in
      ``Integer`` (an instance of :class:`VisitableType`), you'll also get
      ``Integer()`` back. The function asserts that its return type is an
      instance of :class:`TypeEngine`.