code: def test_configure_format(self):
      image = tkinter.PhotoImage("::img::test", master=self.root)
      self.assertEqual(image["format"], "")
      image.configure(file=self.testfile, format="gif")
      self.assertEqual(
          image["format"], ("gif",) if self.wantobjects else "gif"
      )
      self.assertEqual(image.width(), 16)
      self.assertEqual(image.height(), 16)
  
imports: import unittest
  import tkinter
  from test import support
  from test.support import os_helper
  from test.test_tkinter.support import AbstractTkTest, AbstractDefaultRootTest, requires_tk
label_desc: Use image node_id 15 for calling the PhotoImageTest obj's underlying member method code with example usage: obj.test_configure_format() without return types