code: public UnfilledDependency replaceObject(int newObjectIndex) {
      return new UnfilledDependency(subject, subjectSyntax, subjectFunctionVarIndex, subjectArgIndex,
          null, newObjectIndex);
    }
docs: Returns a new UnfilledDependency whose object is {@code newObjectIndex}
  and whose subject is equal to {@code this}'s subject.
  
  @param newObjectIndex
  @return