human
I wrote the below code

    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

What's a good function header?

=====
Here's a good function header?
assistant
#Here's a good function header.

def _AddClearFieldMethod(message_descriptor, cls):