human
Complete the below
def _AddClearFieldMethod(message_descriptor, cls):

    ''''Helper for _AddMessageMethods().'
    '''
assistant
#Here is the Python program you requested.
    def ClearField(self, field_name):
        try:
            field = message_descriptor.fields_by_name[field_name]
        except KeyError:
            raise ValueError(('Protocol    message    has    no    "%s"    field.' % field_name))
        if (field in self._fields):
            del self._fields[field]
        self._Modified()
    cls.ClearField = ClearField