is it a task you are trying to access to or a dataset ? if you need to retrieve a task, you should use Task.get_task()

if i do that :
ds=Dataset.create(dataset_project='datasets',dataset_name='dataset_0')
it will result in the creation of 2 experiments :
results page: the task that corresponds to the script that launched the dataset creation - it will be in PROJECTS/datasets/.datasets/dataset_0 dataset page: the dataset itself : would be in DATASETS/dataset_0