code: protected R setCanDownload(boolean canDownload) {
          JsonObject jsonPermissionsObject = getPermissionsJsonObject();
          jsonPermissionsObject.add(BoxSharedLink.Permissions.FIELD_CAN_DOWNLOAD, canDownload);
          BoxSharedLink.Permissions permissions = new BoxSharedLink.Permissions(jsonPermissionsObject);
  
          JsonObject sharedLinkJsonObject = getSharedLinkJsonObject();
          sharedLinkJsonObject.add(BoxSharedLink.FIELD_PERMISSIONS, permissions.toJsonObject());
          BoxSharedLink sharedLink = new BoxSharedLink(sharedLinkJsonObject);
          mBodyMap.put(BoxItem.FIELD_SHARED_LINK, sharedLink);
          return (R) this;
      }
docs: Sets whether the shared link allows downloads in the request.
  
  @param canDownload   new value for whether the shared link allows downloads.
  @return  request with the updated value for whether the shared link allows downloads.