def convert_to_hetero(item):
    """Utility function to convert homogenous data to heterogenous with a single
    node type."""
    is_heterogenous = isinstance(item, dict)
    return item if is_heterogenous else {"_N": item}
Utility function to convert homogenous data to heterogenous with a single
    node type.
python/dgl/graphbolt/subgraph_sampler.py