Base class for all PFA exceptions (not used directly).
Exception found in the initialization of the PFA document (loading cell/pool data, initializing scoring engine state).
Exception found at runtime in a PFA library function (attempt to get contents of an empty array, etc.
Exception found in the semantics of the PFA document (type mismatches, unrecognized symbols, etc.
Exception found in the syntax of the PFA document (valid JSON but invalid structure for PFA).
Exception raised if a PFA method takes too long.
Exception intentionally raised by the user.