class_docstr: Use of the Python3 'selectors' module.
  
  NOTE: Only use on Python 3.5 or newer!
code: def register(self, fd):
      assert isinstance(fd, int)
      import selectors  # Inline import: Python3 only!
  
      self._sel.register(fd, selectors.EVENT_READ, None)
  
imports: from __future__ import unicode_literals, absolute_import
  import sys
  import abc
  import errno
  import select
  import six
label_desc: Use image node_id 2 for calling the Python3Selector obj's underlying member method code with example usage: obj.register(fd) without return types