AtomicNumberOperators(orbs, groupings) works analogously to CreateAtomicIndicesDict(), but instead of returning a dictionary of indices it returns a dictionary of operators counting the electrons in the corresponding states.
Input
orbs : A list of strings that can be interpreted as atomic orbitals.
groupings : an optional list of orbital groupings each in the format {groupname, {orb1, orb2,…}}.
Output
Num : A dictionary of number operators for the indices corresponding to the orbitals given in orbs, as well as the groups.