code: public int[] deduplicateIntArray(int[] original) {
          if (original == null) return null;
          IntArray intArray = new IntArray(original);
          IntArray canonical = canonicalIntArrays.get(intArray);
          if (canonical == null) {
              canonical = intArray;
              canonicalIntArrays.put(canonical, canonical);
          }
          return canonical.array;
      }
docs: Used to deduplicate time and stop sequence arrays. The same times may occur in many trips.