Regarding snakes in graveyards, great things will happen to future generations. I learned that there has been a popular saying among the people that snakes in graveyards symbolize good luck. This means that among the people, snakes are called "little dragons", and snakes appear in graveyards. It means that this place has sufficient spiritual energy, and the snake sensed it and appeared here. Some people think that this place is a Feng Shui treasure.
However, these are some folk sayings and have no scientific basis, so don't use them. Care too much. In fact, snakes can appear anywhere, such as in some woods, farmland, and some houses, so it is very normal to see snakes in cemeteries.