code: def _create_tautological_expression_for_location(query_metadata_table, location):
      
      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)
docs: For a given location, create a BinaryComposition that always evaluates to 'true'.