How to fix ERROR: "TypeError: set_default_backend() missing 1 required positional argument: 'backend_name'"?

Question

I'm implementing a research paper titled "G-Meta: Graph Meta Learning via Local Subgraphs.

" but whenever i run this

 "!python train.py --data_dir /content/sample_data/california_housing_train.csv --task_setup Disjoint" command it gives an error which is this "Traceback (most recent call last):
  File "/content/G-Meta/G-Meta/train.py", line 10, in <module>
    dgl.backend.set_default_backend('pytorch')

TypeError: set_default_backend() missing 1 required positional argument: 'backend_name'"

If there is any expert please fix it by answering to this question?

I'm trying to complete a research paper implementation today, I'm expecting quick and accurate answers.