If in a binomial distribution, the Bernoulli trials are independent and have different success probabilities, then it is called Poisson Binomial Distribution. Such a question has been previously answered here and here.
How can I do a similar analysis in the case of a multinomial distribution? For instance, if a $k$-sided die is thrown $n$ times and the probabilities of each side showing up changes every time instead of being fixed (as in the case of regular multinomial distribution), how can I calculate the probability mass function of such a distribution? We assume that we have access to $\{\mathbb{p_i}\}_1^n$ where $\mathbb{p_i}$ is a vector of length $k$ denoted the probability of each of the $k$ sides showing up in the $i^{th}$ trial.