code: public static ExtractionFn fromQueryGranularity(final Granularity queryGranularity)
    {
      if (queryGranularity == null) {
        return null;
      } else {
        return new TimeFormatExtractionFn(null, null, null, queryGranularity, true);
      }
    }
docs: Converts a QueryGranularity to an extractionFn, if possible. This is the inverse of
  {@link #toQueryGranularity(ExtractionFn)}. This will always return a non-null extractionFn if
  queryGranularity is non-null.
  
  @param queryGranularity granularity
  
  @return extractionFn, or null if queryGranularity is null