code: def get_headers_from_environ(environ):
    
    headers = wsgiref.headers.Headers([])
    for header, value in environ.iteritems():
      if header.startswith('HTTP_'):
        headers[header[5:].replace('_', '-')] = value
    # Content-Type is special; it does not start with 'HTTP_'.
    if 'CONTENT_TYPE' in environ:
      headers['CONTENT-TYPE'] = environ['CONTENT_TYPE']
    return headers
docs: Get a wsgiref.headers.Headers object with headers from the environment.
  
    Headers in environ are prefixed with 'HTTP_', are all uppercase, and have
    had dashes replaced with underscores.  This strips the HTTP_ prefix and
    changes underscores back to dashes before adding them to the returned set
    of headers.
  
    Args:
      environ: An environ dict for the request as defined in PEP-333.
  
    Returns:
      A wsgiref.headers.Headers object that's been filled in with any HTTP
      headers found in environ.