src/vs/workbench/services/extensions/common/rpcProtocol.ts/MessageIO/serializeRequest
class MessageIO:	public static serializeRequest(req: number, rpcId: number, method: string, serializedArgs: SerializedRequestArguments, usesCancellationToken: boolean): VSBuffer {
		if (serializedArgs.type === 'mixed') {
			return this._requestMixedArgs(req, rpcId, method, serializedArgs.args, serializedArgs.argsType, usesCancellationToken);
		}
		return this._requestJSONArgs(req, rpcId, method, serializedArgs.args, usesCancellationToken);
	}