KeyError Setting Mixture Proportions for Mixture Model

Questions
14 
on_count = 3
schema_count = 10

and I represented them as floats too:

on_count = 3.
schema_count = 10.

but I got the same result.

And for completeness:

pTri_given_on = 1.
pTri_given_not_on = .7
tri_delta_on = pTri_given_on - pTri_given_not_on