code: function ___GEN_OBJECT_ID(initTime=null) {
  	const time	= initTime || Math.floor(Date.now()/1000);
  	const pid	= PID;
  	const inc	= (SEQ_NUMBER=(SEQ_NUMBER+1) % 0xffffff);
  
  
  
  	const buffer = new DataView(new ArrayBuffer(12));
  	
  	// NOTE: Fill in the id information
  	// NOTE: Following statements' order should not be modified!
  	buffer.setUint32(8, inc, false);		// [9-11] seq
  	buffer.setUint16(7, pid, false);		// [7-8] pid
  	buffer.setUint32(3, MACHINE_ID, false);	// [4-6] machine id
  	buffer.setUint32(0, time, false);		// [0-3] epoch time
  	
  	return buffer.buffer;
  }
docs: Generate an array buffer that contains random ObjectId
  @param {Number} [initTime=null]
  @return {ArrayBuffer}
  @private