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())

        offset += 4;

        // Write context name
        System.arraycopy(CONTEXT_NAME_BYTES, 0, buffer, offset, 4);
        offset += 4;

        // Padding to align data to 8-byte boundary
        offset += 4;

        // Write standard lease data (32 bytes)
        leaseKey.encode(buffer, offset); // LeaseKey (16 bytes)
        offset += 16;

        CloseableUtil.close(out);
    }

    private static class NotifyOutputStream extends OutputStream {
        private String notify_;

        @Override
        public void write(final int arg0) throws IOException {
        }

        @Override
        public void close() throws IOException {
            super.close();
            notify_ = "closed";
        }

     * file attributes such as ACLs but it does copy regular attributes as
     * well as create and last write times. This method is almost twice as
     * efficient as manually copying as it employs an additional write
     * thread to read and write data concurrently.
     * <br>
     * It is not possible (nor meaningful) to copy entire workgroups or
     * servers.
     *
     * @param dest

 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package jcifs.pac;

import jcifs.smb.SID;

/**
 * Represents a group membership entry in PAC logon information.

 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package jcifs.pac.kerberos;

import java.util.Map;

import javax.security.auth.kerberos.KerberosKey;

 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package jcifs.netbios;

import jcifs.Configuration;

class NameQueryRequest extends NameServicePacket {

 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package jcifs.smb1.dcerpc.ndr;

/**
 * NDR representation of a hyper integer (8-byte signed integer).
 */