@staticmethod
def _get_list(values):
    """
        Helper method that wraps values in a list. If the input is a list then it is returned. If the input is None then an empty list is returned. For anything else, the input value is wrapped as a single-element list.

        :param values: Value to make sure exists in a list.
        :return: List with the input values.
        """
    if values is None:
        return []
    elif isinstance(values, list):
        return values
    else:
        return [values]
