check if the atoms already have unpaired electrons for a valid combo
check if the atoms already have unpaired electrons for a valid combo

only consider this a valid combination of atoms, if both atoms do not
bear any unpaired electrons.

nickvandewiele/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,chatelak/RMG-Py,pierrelb/RMG-Py,pierrelb/RMG-Py