• Closes 11643
• Tests added / passed

Tests for the bags module pass:

Tests for the utils module pass:

• Passes pre-commit run --all-files

How did I verify that the fix works:

I recreated the test mentioned in the issue above, here's the code:

 if __name__ == "__main__":
    import dask.bag as db
    import numpy as np
    from dask import delayed
    from scipy.sparse import csr_array


    def add(x, y):
        return x + y


    @delayed
    def create_sparse_array_delayed():
        return csr_array(np.random.random((10, 10)))


    @delayed
    def create_array_delayed():
        return np.random.random((10, 10))


    db.from_sequence(
        [csr_array(np.random.random((10, 10))), csr_array(np.random.random((10, 10)))]).fold(
        add).compute()  # works with sparse arrays when created from sequence
    db.from_delayed([create_array_delayed(), create_array_delayed()]).fold(add).compute()  # works with numpy arrays
    print(db.from_delayed([create_sparse_array_delayed(), create_sparse_array_delayed()]).fold(add).compute()) 

This now returns the result instead of the bug: