inner class FaultySink(
    sink: Sink,
    private val file: Path,
  ) : ForwardingSink(sink) {
    override fun write(
      source: Buffer,
      byteCount: Long,
    ) {
      if (writeFaults.contains(file)) {
        throw IOException("boom!")
      } else {
        super.write(source, byteCount)
      }
    }
  }

		if globalServerCtxt.CrossDomainXML != "" {
			cxml = globalServerCtxt.CrossDomainXML
		}
		// Look for 'crossdomain.xml' in the incoming request.
		if r.URL.Path == crossDomainXMLEntity {
			// Write the standard cross domain policy xml.
			w.Write([]byte(cxml))
			// Request completed, no need to serve to other handlers.
			return
		}
		h.ServeHTTP(w, r)
	})

  }

  /**
   * We had a bug where the cache was left in an inconsistent state after a journal write failed.
   * https://github.com/square/okhttp/issues/1211
   */
  @Test
  fun journalWriteFailsDuringEditorCommit() {
    set("a", "a", "a")
    set("b", "b", "b")

    // Create an entry that fails to write to the journal during commit.
    val editor = cache.edit("c")!!
    editor.setString(0, "c")

    ByteBufferHasher(int expectedInputSize) {
      this.buffer = ByteBuffer.allocate(expectedInputSize).order(ByteOrder.LITTLE_ENDIAN);
    }

    /**
     * Resizes the buffer if necessary. Guaranteed to leave `buffer` in Write Mode ready for new
     * data.
     */
    private void ensureCapacity(int needed) {
      if (buffer.remaining() >= needed) {
        return;
      }

      int currentCapacity = buffer.capacity();

from typing import Annotated

from fastapi import BackgroundTasks, Depends, FastAPI

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: str | None = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q

from typing import Union

from fastapi import BackgroundTasks, Depends, FastAPI

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: Union[str, None] = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q

          throw ProtocolException("unexpected address: " + toSocket.localAddress)
        }

        // Write the reply.
        fromSink.writeByte(VERSION_5)
        fromSink.writeByte(REPLY_SUCCEEDED)
        fromSink.writeByte(0)
        fromSink.writeByte(ADDRESS_TYPE_IPV4)
        fromSink.write(localAddress)
        fromSink.writeShort(toSocket.localPort)
        fromSink.emit()

It is just a standard function that can receive parameters.

It can be an `async def` or normal `def` function, **FastAPI** will know how to handle it correctly.

In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

{* ../../docs_src/background_tasks/tutorial001_py39.py hl[6:9] *}

	setEventStreamHeaders(w)

	// Listen Publisher and peer-listen-client uses nonblocking send and hence does not wait for slow receivers.
	// Use buffered channel to take care of burst sends or slow w.Write()
	mergeCh := make(chan []byte, globalAPIConfig.getRequestsPoolCapacity()*len(globalEndpoints.Hostnames()))
	localCh := make(chan event.Event, globalAPIConfig.getRequestsPoolCapacity())

    writer: DerWriter,
    value: T,
  ) {
    if (typeHint) {
      writer.typeHint = value
    }

    if (isOptional && value == defaultValue) {
      // Nothing to write!
      return
    }

    writer.write(name, tagClass, tag) {
      codec.encode(writer, value)
    }
  }

  /**
   * Returns a copy with a context tag. This should be used when the type is ambiguous on its own.