*
   * This method returns false unless it is overridden by a subclass.
   *
   * ### Duplex Transmission
   *
   * With regular HTTP calls the request always completes sending before the response may begin
   * receiving. With duplex the request and response may be interleaved! That is, request body bytes
   * may be sent after response headers or body bytes have been received.
   *

CAREFUL: When utilizing two-way communication, it is important to ensure that the remote handler is not blocked on a send.
If the remote handler is blocked on a send, and the client is trying to send without the remote receiving,
the operation would become deadlocked if the channels are full.

### Typed handlers

Typed handlers are handlers that have a specific type for the request and response payloads.

```go

                                 n_ask_attempts=_DEFAULT_PROMPT_ASK_ATTEMPTS):
  """Loop over user prompts for an ENV param until receiving a valid response.

  For the env param var_name, read from the environment or verify user input
  until receiving valid input. When done, set var_name in the environ_cp to its
  new value.

  Args:
    environ_cp: (Dict) copy of the os.environ.

   * This was misleading for tracing because it was too early.
   */
  open fun responseHeadersStart(call: Call) {
  }

  /**
   * Invoked immediately after receiving response headers.
   *
   * This method is always invoked after [responseHeadersStart].
   *
   * @param response the response received over the network. It is an error to access the body of
   *     this response.

        // Tree handle is released after close
        verify(tree, atLeastOnce()).release();
    }

    @Test
    @DisplayName("open(): server returns NO_SUCH_FILE after receiving response -> iterator empty, closed")
    void openHandlesNoSuchFileGracefully() throws Exception {
        when(tree.send(any(Trans2FindFirst2.class), any(Trans2FindFirst2Response.class))).thenAnswer((InvocationOnMock inv) -> {

    // retry, we return true and try a new route.
    return true
  }

  /**
   * Figures out the HTTP request to make in response to receiving [userResponse]. This will
   * either add authentication headers, follow redirects or handle a client request timeout. If a
   * follow-up is either unnecessary or not applicable, this returns null.
   */

 * This class simplifies communication for protocols that support
 * multiplexing requests. It encapsulates a stream and some protocol
 * knowledge (provided by a concrete subclass) so that connecting,
 * disconnecting, sending, and receiving can be syncronized
 * properly. Apparatus is provided to send and receive requests
 * concurrently.
 */

public abstract class Transport implements Runnable {

    /**
     * Default constructor for Transport.

{* ../../docs_src/path_params/tutorial003_py39.py hl[6,11] *}

Otherwise, the path for `/users/{user_id}` would match also for `/users/me`, "thinking" that it's receiving a parameter `user_id` with a value of `"me"`.

Similarly, you cannot redefine a path operation:

{* ../../docs_src/path_params/tutorial003b_py39.py hl[6,11] *}

    private static final String WITNESS_SERVICE_UUID = "ccd8c074-d0e5-4a40-92b4-d074faa6ba28";
    private static final int DEFAULT_WITNESS_PORT = 135; // RPC endpoint mapper

    /**
     * Interface for receiving witness notifications and registration events.
     */
    public interface WitnessNotificationListener {
        /**
         * Called when a witness notification is received.
         *

// An optional error can be sent which will be picked as text only error,
// without its original type by the receiver.
// waitForHTTPResponse should be used to the receiving side.
func keepHTTPReqResponseAlive(w http.ResponseWriter, r *http.Request) (resp func(error), body io.ReadCloser) {
	bodyDoneCh := make(chan struct{})
	doneCh := make(chan error)
	ctx := r.Context()
	go func() {