code: def match_any(self, match):
          
          match_key = '_id'
          param = '$exists'
          if match:
              flag = 'true'
          else:
              flag = 'false'
          if match_key in self._query_terms:
              self._query_terms[match_key][param] = flag
          else:
              self._query_terms[match_key] = {param: flag}
docs: Matches any object.
  
          arg:    match (boolean): ``true`` to match any object ``,``
                  ``false`` to match no objects
          *compliance: mandatory -- This method must be implemented.*