code: function simplify(node, debug=false) {
    if(checks.hasUnsupportedNodes(node)) {
      return node;
    }
  
    const steps = stepThrough(node, debug);
    let simplifiedNode;
    if (steps.length > 0) {
      simplifiedNode = steps.pop().newNode;
    }
    else {
      // removing parens isn't counted as a step, so try it here
      simplifiedNode = removeUnnecessaryParens(flattenOperands(node), true);
    }
    // unflatten the node.
    return unflatten(simplifiedNode);
  }
docs: Given a mathjs expression node, steps through simplifying the expression. Returns the simplified expression node.