Calculating the branching ratio from an excited state down to another state.

[TanAndMichaelLover112]

Hello,
I have a question about the .getBranchingRatio function for an atom. I need to understand the branching ratios from one state, an S state, down to a lower P state for example (nS1/2 -> n-4 P1/2, or something). The only other discussion on this function focused only on the hyperfine transition rate.
Is there any example of this being used in a calculation. If this isn't the correct function for my purpose could someone point me in the right direction with an example (if possible?).
The documentation seems to have an error for .getBranchingRatio but I interpreted it as;
jg as total orbital momentum
fg total atomic angular momentum
mfg as the projection
all for ground state (and the values ending in e are the excited)
but then after inputting my calculations the function asks for only integer/half-integers so I stuck to using the quantum numbers L, S and addition of both but keep getting 'j0' as my answer.
Is there any chance someone could help me understand this/what values are needed?
Much appreciated,
(sorry if my English is bad)