'Helper method to get all values of a URL query variable
@param get_vars: the GET vars (a dict)
@param variable: the name of the query variable
@return: a list of values'

@staticmethod
def _values(get_vars, variable):

    if (not variable):
        return []
    elif (variable in get_vars):
        values = S3URLQuery.parse_value(get_vars[variable])
        if (not isinstance(values, (list, tuple))):
            values = [values]
        return values
    else:
        return []
