docstr: Return a Junit node containing custom properties, if any.
          
code: def _get_global_properties_node(self):
      """Return a Junit node containing custom properties, if any."""
      if self.global_properties:
          return Junit.properties(
              [
                  Junit.property(name=name, value=value)
                  for name, value in self.global_properties
              ]
          )
      return ""
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import functools
  import os
  import platform
  import re
  import sys
  import time
  from datetime import datetime
  import py
  import six
  import pytest
  from _pytest import nodes
  from _pytest.config import filename_arg
label_desc: Use image node_id 14 for calling the LogXML obj's underlying member method code with example usage: obj._get_global_properties_node() and returns: str, Junit