code: public static double convertLength(@FloatRange(from = 0) double distance,
                                       @NonNull @TurfUnitCriteria String originalUnit,
                                       @Nullable @TurfUnitCriteria String finalUnit) {
      if (finalUnit == null) {
        finalUnit = TurfConstants.UNIT_DEFAULT;
      }
      return radiansToLength(lengthToRadians(distance, originalUnit), finalUnit);
    }
docs: Converts a distance to a different unit specified.
  
  @param distance     the distance to be converted
  @param originalUnit of the distance, must be one of the units defined in
  {@link TurfUnitCriteria}
  @param finalUnit    returned unit, {@link TurfConstants#UNIT_DEFAULT} if not specified
  @return the converted distance
  @since 2.2.0