code: def format_metadata(self, dist):
      sio = StringIO.StringIO()
      dist.metadata.write_pkg_file(sio)
      return sio.getvalue()
  
imports: import os
  import StringIO
  import sys
  import unittest
  import warnings
  import textwrap
  from distutils.dist import Distribution, fix_help_options
  from distutils.cmd import Command
  import distutils.dist
  from test.test_support import TESTFN, captured_stdout, run_unittest, unlink
  from distutils.tests import support
  from distutils import log
label_desc: Use image node_id 13 for calling the MetadataTestCase obj's underlying member method code with example usage: obj.format_metadata(dist) and returns: sio