code: def get_request_query(self):
          
          query = {}
  
          # only known indexes get observed
          indexes = self.catalog.get_indexes()
  
          for index in indexes:
              # Check if the request contains a parameter named like the index
              value = req.get(index)
              # No value found, continue
              if value is None:
                  continue
              # Convert the found value to format understandable by the index
              index_value = self.catalog.to_index_value(value, index)
              # Conversion returned None, continue
              if index_value is None:
                  continue
              # Append the found value to the query
              query[index] = index_value
  
          return query
docs: Checks the request for known catalog indexes and converts the values
          to fit the type of the catalog index.
  
          :param catalog: The catalog to build the query for
          :type catalog: ZCatalog
          :returns: Catalog query
          :rtype: dict