pylint #3123 W0212 false positive on static method [resolved]

Duncan reported :

class Thing(object):
  ''' example class '''

  _next_id = 0

  __slots__ = ('number', 'name')

  def __init__(self, name):
      self.number = Thing.next_id()
      self.name   = name

  def __str__(self):
      return '(number=%d, name="%s")' % (self.number, self.name)

  def next_id():
      ''' static method to increment "private" class attribute '''
      Thing._next_id += 1
      return Thing._next_id
  next_id = staticmethod(next_id)

gives :

W: 20:Thing.next_id: Access to a protected member _next_id of a client class
W: 21:Thing.next_id: Access to a protected member _next_id of a client class