code: public ItemRequest<Task> update(String task) {
      
          String path = String.format("/tasks/%s", task);
          return new ItemRequest<Task>(this, Task.class, path, "PUT");
      }
docs: A specific, existing task can be updated by making a PUT request on the
  URL for that task. Only the fields provided in the `data` block will be
  updated; any unspecified fields will remain unchanged.
  
  When using this method, it is best to specify only those fields you wish
  to change, or else you may overwrite changes made by another user since
  you last retrieved the task.
  
  Returns the complete updated task record.
  
  @param  task The task to update.
  @return Request object