@Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;

    Constraint that = (Constraint)o;

    if (calls != that.calls) return false;
    if (nulls != that.nulls) return false;

    return true;
  }
@Override
  public boolean equals(Object o)