code: def verify_roster_result(self, fix = False):
          
          self._verify((None, u"from", u"to", u"both"), fix)
docs: Check if `self` is valid roster item.
  
          Valid item must have proper `subscription` value other than 'remove'
          and valid value for 'ask'.
  
          :Parameters:
              - `fix`: if `True` than replace invalid 'subscription' and 'ask'
                values with the defaults
          :Types:
              - `fix`: `bool`
  
          :Raise: `ValueError` if the item is invalid.