code: def indent(self, elem, level=0):
      # in-place prettyprint formatter
      i = "\n" + "  " * level
      if len(elem):
          if not elem.text or not elem.text.strip():
              elem.text = i + "  "
          if not elem.tail or not elem.tail.strip():
              elem.tail = i
          for elem in elem:
              self.indent(elem, level + 1)
          if not elem.tail or not elem.tail.strip():
              elem.tail = i
      else:
          if level and (not elem.tail or not elem.tail.strip()):
              elem.tail = i
  
imports: import itertools
  import time
  from xml.etree.ElementTree import Element, ElementTree, SubElement, register_namespace, tostring
  import networkx
  from networkx.utils import open_file
label_desc: Use image node_id 14 for calling the GEXFWriter obj's underlying member method code with example usage: obj.indent(elem, level) without return types