code: def to_query(self):
          
          query = {}
          for filter_instance in self.filters:
              if filter_instance.is_empty():
                  continue
              filter_query = filter_instance.to_query()
              query.update(filter_query)
  
          return query
docs: Iterates over all filters and converts them to an Elastic HTTP API
          suitable query.
  
          Note: each :class:`~es_fluent.filters.Filter` is free to set it's own
          filter dictionary. ESFluent does not attempt to guard against filters
          that may clobber one another.  If you wish to ensure that filters are
          isolated, nest them inside of a boolean filter such as
          :class:`~es_fluent.filters.core.And` or
          :class:`~es_fluent.filters.core.Or`.