setting n_jobs != 1 raises ValueError: not enough values to unpack (expected 3, got 2)

[DeeliN221]

Hi, in the given example file examples/radical_distribution_function.ipynb, setting n_jobs !=1 caused ValueError: not enough values to unpack (expected 3, got 2)

This error make the fast rdf functions less appealing and practically slow down the calculation.

Hope this be fixed some day.