"helper function" style question

[Robert Ferrell]

I have a style question.  I have a class with a method, m1, which
needs a helper function, hf.  I can put hf inside m1, or I can make it
another method of the class.  The only place hf should ever be invoked
is from inside m1.

Is either style preferred?

Here are two short examples:

Helper function as method:

class K(object):
  def _hf(self):
    print 'Yo'
  def m1(self):
    self._hf()
    return

Helper function as "private" function inside m1.

class K(object):
  def m1(self):
    def hf():
      print 'Yo'
    hf()
    return

Opinions greatly appreciated.

thanks,
-robert