code: def unsearchable_fields(self):
          
          filter_func = lambda field: not field.is_searchable
          return filter(filter_func, self.names) + \
                 filter(filter_func, self.emails) + \
                 filter(filter_func, self.phones) + \
                 filter(filter_func, self.usernames) + \
                 filter(filter_func, self.addresses) + \
                 filter(filter_func, self.dobs)
docs: A list of all the fields that can't be searched by.
          
          For example: names/usernames that are too short, emails that are 
          invalid etc.