docs: function uploadAttachment(attachment) {
    return new Promise (async (resolve, reject) => {
      if (!attachment) {
        reject('Valid attachment object required');
      }
  
      let request_options = {
        'path': '/me/message_attachments'
      };
  
      let AttachmentPayload = new util.AttachmentPayload(attachment);
  
      if (!AttachmentPayload) reject('Valid URL or file required');
  
      if (AttachmentPayload.formData) {
        request_options.formData = AttachmentPayload.formData;
      } else {
        request_options.payload = { 'message': AttachmentPayload };
      }
  
      try {
        let response = await this.sendGraphRequest(request_options);      
        resolve(response);
      } catch (e) {
        reject(e);
      }
    });
  }