code: function callSendApi (recipient, payload) {  
    return new Promise (async (resolve, reject) => {
      if (!recipient) {
        reject('recipient object required');
      }
  
      if (!payload) {
        reject('payload required');      
      }
  
      let request_options = { 'path': '/me/messages' };
  
      if (payload.formData) {
        request_options.formData = payload.formData;
      } else {
        request_options.payload = new util.RequestPayload(recipient, payload);  
        if (!request_options.payload) reject('error creating request payload');      
      }
      
      try {    
        let response = await this.sendGraphRequest(request_options);  
        resolve(response);
      } catch (e) {
        reject(e);
      }
    });
  }
docs: /* API Request