code: public int getLengthDelta() {
          int delta = 0;
  
          for (int mut : mutations)
              switch (mut & MUTATION_TYPE_MASK) {
                  case RAW_MUTATION_TYPE_DELETION:
                      --delta;
                      break;
                  case RAW_MUTATION_TYPE_INSERTION:
                      ++delta;
                      break;
              }
  
          return delta;
      }
docs: Returns the difference between the length of initial sequence and length of mutated sequence. Negative values
  denotes that mutated sequence is shorter.
  
  @return difference between the length of initial sequence and mutated sequence