code: def alter_graph_mode_timeformat(self, start_or_end):
      # If 'start' or 'end' appears, alter Graph mode to dynamic and
      # set timeformat
      if self.graph_element.get("mode") == "static":
          if start_or_end is not None:
              if isinstance(start_or_end, str):
                  timeformat = "date"
              elif isinstance(start_or_end, float):
                  timeformat = "double"
              elif isinstance(start_or_end, int):
                  timeformat = "long"
              else:
                  raise nx.NetworkXError(
                      "timeformat should be of the type int, float or str"
                  )
              self.graph_element.set("timeformat", timeformat)
              self.graph_element.set("mode", "dynamic")
  
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 12 for calling the GEXFWriter obj's underlying member method code with example usage: obj.alter_graph_mode_timeformat(start_or_end) without return types