code: def put_headers_in_environ(headers, environ):
    
    for key, value in headers:
      environ['HTTP_%s' % key.upper().replace('-', '_')] = value
docs: Given a list of headers, put them into environ based on PEP-333.
  
    This converts headers to uppercase, prefixes them with 'HTTP_', and
    converts dashes to underscores before adding them to the environ dict.
  
    Args:
      headers: A list of (header, value) tuples.  The HTTP headers to add to the
        environment.
      environ: An environ dict for the request as defined in PEP-333.