code: public static double length(@NonNull MultiLineString multiLineString,
                                @NonNull @TurfConstants.TurfUnitCriteria String units) {
      double len = 0;
      for (List<Point> points : multiLineString.coordinates()) {
        len += length(points, units);
      }
      return len;
    }
docs: Takes a {@link MultiLineString} and measures its length in the specified units.
  
  @param multiLineString geometry to measure
  @param units           one of the units found inside {@link TurfConstants.TurfUnitCriteria}
  @return length of the input lines combined, in the units specified
  @see <a href="http://turfjs.org/docs/#linedistance">Turf Line Distance documentation</a>
  @since 1.2.0