code: def getNameByPosition(self, idx):
          
          try:
              return self.__namedTypes[idx].name
  
          except IndexError:
              raise error.PyAsn1Error('Type position out of range')
docs: Return field name by its position in fields set.
  
          Parameters
          ----------
          idx: :py:class:`idx`
              Field index
  
          Returns
          -------
          : :py:class:`str`
              Field name
  
          Raises
          ------
          : :class:`~pyasn1.error.PyAsn1Error`
              If given field name is not present in callee *NamedTypes*