Internal function for accessing a member function (method) of a nimbleFunction. Normally a user will write nf$method(x) instead of nfMethod(nf, method)(x).
nfMethod(nf, methodName)a specialized nimbleFunction, i.e. one that has already had setup parameters processed
a character string giving the name of the member function to call
a function that can be called.
nimbleFunctions have a default member function called run, and may have other member functions provided via the methods argument to nimbleFunction.
As an internal step, the NIMBLE compiler turns nf$method(x) into nfMethod(nf, method)(x), but a NIMBLE user or programmer would not normally need to use nfMethod directly.