class_docstr: base class for Collector and Item the test collection tree.
  Collector subclasses have children, Items are terminal nodes.
docstr: Return a set of all extra keywords in self and any parents.
docstr_tok: ["Return","a","set","of","all","extra","keywords","in","self","and","any","parents","."]
code: def listextrakeywords(self):
      """Return a set of all extra keywords in self and any parents."""
      extra_keywords = set()
      for item in self.listchain():
          extra_keywords.update(item.extra_keyword_matches)
      return extra_keywords
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import warnings
  import py
  import six
  import _pytest._code
  from _pytest.compat import getfslineno
  from _pytest.mark.structures import NodeKeywords
  from _pytest.outcomes import fail
label_desc: Use image node_id 14 for calling the Node obj's underlying member method code with example usage: obj.listextrakeywords() and returns: extra_keywords