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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def postprocess_html(html, metadata):
 """Returns processed HTML to fit into the slide template format."""

  if metadata.get('build_lists') and metadata['build_lists'] == 'true':
    html = html.replace('<ul>', '<ul class="build">')
    html = html.replace('<ol>', '<ol class="build">')
  return html