code: @Override
      public Positions merge(Positions other) {
  
          if (other instanceof SinglePosition) {
              SinglePosition that = (SinglePosition) other;
              return LinearPositions.builder().addSinglePosition(this).addSinglePosition(that).build();
          } else {
              return other.merge(this);
          }
      }
docs: Merge this SinglePosition with another {@link Positions} instance. If the given {@link Positions} is:
  - a SinglePosition, it returns a {@link LinearPositions} composed by this and the given positions, in order.
  - any other {@link Positions}, it delegates to the given {@link Positions} merge.
  
  @param other Positions instance to merge with.
  
  @return Positions instance result of merge.