def validate(self, value):
    value = super(ListProperty, self).validate(value)
    if value is not None:
      if not isinstance(value, list):
        raise BadValueError('Property %s must be a list' % self.name)

      value = self.validate_list_contents(value)
    return value
Validate list.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/db/__init__.py/ListProperty.validate