When animated, if both the beginning and end filters have a function list of the same length without url()
in the same order, each of their filter functions is interpolated according to the filter function's specific rules.
If the filter lists are of different lengths, the missing equivalent filter functions from the longer list are added to the end of the shorter list. The added functions use their initial, no filter modification values. All the filters listed are then interpolated according to the filter function's specific rules. Otherwise, discrete interpolation is used.