docs: def get_headers(params, boundary):
      """Returns a dictionary with Content-Type and Content-Length headers
      for the multipart/form-data encoding of ``params``."""
      headers = {}
      boundary = urllib.quote_plus(boundary)
      headers['Content-Type'] = "multipart/form-data; boundary=%s" % boundary
      headers['Content-Length'] = str(get_body_size(params, boundary))
      return headers