Recall that each symbol in the HMM is represented by a unique integer-valued
number. This method assumes the system is in steady state, and calculates the
long term time average (when ) of the values of the emitted
symbols. In other words, it calculates the expected symbol value that will be
observed in one symbol emission.
Usages: symb_tavg()
Output: Prints the symbol's average value emitted, over time, when .