code: function groupCoefficientsForAdding(node) {
    let newNode = clone(node);
  
    const polynomialTermList = newNode.args.map(n => new Node.PolynomialTerm(n));
    const coefficientList = polynomialTermList.map(p => p.getCoeffNode(true));
    const sumOfCoefficents = Node.Creator.parenthesis(
      Node.Creator.operator('+', coefficientList));
    // TODO: changegroups should also be on the before node, on all the
    // coefficients, but changegroups with polyTerm gets messy so let's tackle
    // that later.
    sumOfCoefficents.changeGroup = 1;
  
    // Polynomial terms that can be added together must share the same symbol
    // name and exponent. Get that name and exponent from the first term
    const firstTerm = polynomialTermList[0];
    const exponentNode = firstTerm.getExponentNode();
    const symbolNode = firstTerm.getSymbolNode();
    newNode = Node.Creator.polynomialTerm(
      symbolNode, exponentNode, sumOfCoefficents);
  
    return Node.Status.nodeChanged(
      ChangeTypes.GROUP_COEFFICIENTS, node, newNode);
  }
docs: Given a sum of like polynomial terms, groups the coefficients e.g. 2x^2 + 3x^2 + 5x^2 -> (2+3+5)x^2 Returns a Node.Status object.