text: """Modify an HTTP form submission."""
  from mitmproxy import http
  
  
  def request(flow: http.HTTPFlow) -> None:
      if flow.request.urlencoded_form:
          # If there's already a form, one can just add items to the dict:
          flow.request.urlencoded_form["mitmproxy"] = "rocks"
      else:
          # One can also just pass new form data.
          # This sets the proper content type and overrides the body.
          flow.request.urlencoded_form = [
              ("foo", "bar")
          ]
  