Moved validation of input Y to function timeSeriesValidator.
Added show method for FrequencyRepresentation.
Fixed the documentation of timeSeriesValidator.
Revert "Fixed the documentation of timeSeriesValidator."

This reverts commit cbe241d78dc21fefcf4729baa876a590fe57c78b.
Revert "Revert "Fixed the documentation of timeSeriesValidator.""

This reverts commit 33159ae1fcebfc256473a72d3c45e02a9893c3be.