code: def append(self, ldap_filter):
          
          if not isinstance(ldap_filter, (LDAPFilter, LDAPCriteria)):
              raise TypeError(
                  "Invalid filter type: {0}".format(type(ldap_filter).__name__)
              )
  
          if len(self.subfilters) >= 1 and self.operator == NOT:
              raise ValueError("Not operator only handles one child")
  
          self.subfilters.append(ldap_filter)
docs: Appends a filter or a criterion to this filter
  
          :param ldap_filter: An LDAP filter or criterion
          :raise TypeError: If the parameter is not of a known type
          :raise ValueError: If the more than one filter is associated to a
                             NOT operator