@classmethod
def from_json_upstream(cls, json_data):
    """
        Initializes a value object from json_data that's been fetched for upstream data.

        :param json_data: JSON-data that initialize the object.
        :type json_data: dict
        """
    field_id = json_data.keys()[0]
    value = json_data[field_id]
    return cls(field_id=field_id, value=value)
