code: def ListOf(element_type, element_none_value=None):
      
      from pyws.functions.args.types import TypeFactory
      element_type = TypeFactory(element_type)
      return type(element_type.__name__ + 'List', (List,), {
          'element_type': element_type,
          'element_none_value': element_none_value})
docs: This function creates a list type with element type ``element_type`` and an
      empty element value ``element_none_value``.
  
      >>> from pyws.functions.args import Integer, ListOf
      >>> lst = ListOf(int)
      >>> issubclass(lst, List)
      True
      >>> lst.__name__
      'IntegerList'
      >>> lst.element_type == Integer
      True