code: def test_download_url(self):
      attrs = {
          "name": "Boa",
          "version": "3.0",
          "download_url": "http://example.org/boa",
      }
      dist = Distribution(attrs)
      meta = self.format_metadata(dist)
      self.assertIn("Metadata-Version: 1.1", meta)
  
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 4 for calling the MetadataTestCase obj's underlying member method code with example usage: obj.test_download_url() without return types