A Pacer, or pacing function, maps one double value to another; they
are used to parameterize animation rates, where the input value f moves
from 0 to 1 linearly, but the returned output can vary quite differently
in response to the input.
Factory class that maintains a collection of parser instances and returns
the appropriate parser based on a history of samples presented to the
factory.
Creates a PolarLocationAnimator that operates on VisualItems
within the specified group, while using regular linear interpolation
(in Cartesian (x,y) coordinates rather than polar coordinates) for
items also contained within the specified linearGroup.