How to use the child_process._forkChild function in child_process

E._create_ipc_channel = fd=>{
    // save process so we can restore it after _forkChild() changed it
    let original_process = process;
    try {
        let channel = global.process = new EventEmitter();
        child_process._forkChild(fd);
        // fixing node bug:
        // recv handle loss when msg is splitted into multiple chunks
        let pipe = channel._channel, orig_onread = pipe.onread, last_handle;
        pipe.onread = (nread, pool, handle)=>{
            last_handle = handle||last_handle;
            return orig_onread.call(pipe, nread, pool, last_handle);
        };
        channel.on('internalMessage', (msg, handle)=>{
            if (handle===last_handle)
                last_handle = null;
        });
        return channel;
    } finally { global.process = original_process; }
};
E.create_socket_pair = ()=>etask(function*create_socket_pair(){

function setupChildProcessIpcChannel() {
  if (process.env.NODE_CHANNEL_FD) {
    const assert = require('internal/assert');

    const fd = parseInt(process.env.NODE_CHANNEL_FD, 10);
    assert(fd >= 0);

    // Make sure it's not accidentally inherited by child processes.
    delete process.env.NODE_CHANNEL_FD;

    require('child_process')._forkChild(fd);
    assert(process.send);
  }
}

function setupChildProcessIpcChannel() {
  if (process.env.NODE_CHANNEL_FD) {
    const assert = require('internal/assert');

    const fd = parseInt(process.env.NODE_CHANNEL_FD, 10);
    assert(fd >= 0);

    // Make sure it's not accidentally inherited by child processes.
    delete process.env.NODE_CHANNEL_FD;

    require('child_process')._forkChild(fd);
    assert(process.send);
  }
}

// start parsing data from that stream.
  if (process.env.NODE_CHANNEL_FD) {
    const fd = parseInt(process.env.NODE_CHANNEL_FD, 10);
    assert(fd >= 0);

    // Make sure it's not accidentally inherited by child processes.
    delete process.env.NODE_CHANNEL_FD;

    const cp = require('child_process');

    // Load tcp_wrap to avoid situation where we might immediately receive
    // a message.
    // FIXME is this really necessary?
    process.binding('tcp_wrap');

    cp._forkChild(fd);
    assert(process.send);
  }
}