Implement the emission_probability method which takes a string, a mapping from letter to index, a mapping from hidden path letter to index, a transition matrix and an emission matrix.
The function should return the probability of any hidden path emitting the given emission.
>>> emission_probability('yyyyzyxxxy', {'y': 1, 'z': 2, 'x': 0}, {'A': 0, 'B': 1}, [[0.2915439583949658, 0.7084560416050342], [0.5443249998401023, 0.4556750001598978]], [[0.6496850841876853, 0.13086798248939702, 0.2194469333229175], [0.17166446158695747, 0.681506463779169, 0.14682907463387349]]) 5.413522108545051e-05 >>> emission_probability('xxyyyyyyyzyyxzy', {'y': 1, 'z': 2, 'x': 0}, {'A': 0, 'B': 1}, [[0.6561529475386385, 0.3438470524613615], [0.601103149430435, 0.398896850569565]], [[0.3655236115728247, 0.33617424673865615, 0.29830214168851915], [0.5793559570923476, 0.30813438342020955, 0.11250965948744292]]) 6.720073375315333e-08