### Async Context Manager

If you check, the function is decorated with an `@asynccontextmanager`.

That converts the function into something called an "**async context manager**".

{* ../../docs_src/events/tutorial003.py hl[1,13] *}

A **context manager** in Python is something that you can use in a `with` statement, for example, `open()` can be used as a context manager:

    } catch (NoSuchFileException e) {
      try {
        Files.createFile(path);
      } catch (FileAlreadyExistsException ignore) {
        // The file didn't exist when we called setLastModifiedTime, but it did when we called
        // createFile, so something else created the file in between. The end result is
        // what we wanted: a new file that probably has its last modified time set to approximately

    } catch (NoSuchFileException e) {
      try {
        Files.createFile(path);
      } catch (FileAlreadyExistsException ignore) {
        // The file didn't exist when we called setLastModifiedTime, but it did when we called
        // createFile, so something else created the file in between. The end result is
        // what we wanted: a new file that probably has its last modified time set to approximately

bsbhv     : base behaviors
bsentity  : base entities
cbean     : condition-beans (both base and extended)
exbhv     : extended behaviors
exentity  : extended entities
- - - - - - - - - -/

For example, if a table called "MEMBER" exists,
you can use these classes like this:
/- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
memberBhv.selectEntity(cb -> {
    cb.query().setMemberId_Equal(3);
}).alwaysPresent(member -> {

	//
	// 1. If a writer.write() returns false, select loop below exits and
	// closes `doneCh` to indicate to caller to also exit.
	//
	// 2. If caller (Evaluate()) has an error, it sends an error
	// message and waits for this go-routine to quit in
	// FinishWithError()
	//
	// 3. If caller is done, it waits for this go-routine to exit
	// in Finish()

	quitFlag := false
	for !quitFlag {
		select {

        return disconnect(hard, true);
    }


    /**
     * Disconnect the transport
     * 
     * @param hard
     * @param inUse
     *            whether the caller is holding a usage reference on the transport
     * @return whether conenction was in use
     * @throws IOException
     */
    public synchronized boolean disconnect ( boolean hard, boolean inUse ) throws IOException {

    delegate.responseBodyEnd(call, byteCount)
  }

  override fun responseFailed(
    call: Call,
    ioe: IOException,
  ) {
    logWithTime("responseFailed: $ioe")

    delegate.responseFailed(call, ioe)
  }

  override fun callEnd(call: Call) {
    logWithTime("callEnd")

    delegate.callEnd(call)
  }

  override fun callFailed(
    call: Call,

  }

  /** Throw {@link IllegalStateException} if {@link #createTestSuite()} can't be called yet. */
  protected void checkCanCreate() {
    if (subjectGenerator == null) {
      throw new IllegalStateException("Call using() before createTestSuite().");
    }
    if (name == null) {
      throw new IllegalStateException("Call named() before createTestSuite().");
    }
    if (features == null) {

        return new BiMapEntry(entry);
      }

      @Override
      public void remove() {
        if (entry == null) {
          throw new IllegalStateException("no calls to next() since the last call to remove()");
        }
        V value = entry.getValue();
        iterator.remove();
        removeFromInverseMap(value);
        entry = null;
      }
    };
  }

  @WeakOuter

     */
    int invoke(@Nonnull R invokerRequest) throws InvokerException;

    /**
     * Closes and disposes of this {@link Invoker} instance, releasing any resources it may hold.
     * This method is called automatically when using try-with-resources statements.
     *
     * <p>The default implementation does nothing. Subclasses should override this method
     * if they need to perform cleanup operations.</p>
     *