code: public static double radiansToLength(double radians, @NonNull @TurfUnitCriteria String units) {
      return radians * FACTORS.get(units);
    }
docs: Convert a distance measurement (assuming a spherical Earth) from radians to a more friendly
  unit.
  
  @param radians a double using unit radian
  @param units   pass in one of the units defined in {@link TurfUnitCriteria}
  @return converted radian to distance value
  @since 1.2.0