For a given location, create a BinaryComposition that always evaluates to 'true'.

def _create_tautological_expression_for_location(query_metadata_table, location):
    """For a given location, create a BinaryComposition that always evaluates to 'true'."""
    location_type = query_metadata_table.get_location_info(location).type

    location_exists = BinaryComposition(
        u'!=', ContextField(location, location_type), NullLiteral)
    location_does_not_exist = BinaryComposition(
        u'=', ContextField(location, location_type), NullLiteral)
    return BinaryComposition(u'||', location_exists, location_does_not_exist)