Function addToLookup

src/traces/sunburst/calc.js:30–34

(parent, v)

    var parent2children = {};
    var refs = {};
    var addToLookup = function(parent, v) {
        if(parent2children[parent]) parent2children[parent].push(v);
        else parent2children[parent] = [v];
        refs[v] = 1;
    };

    // treat number `0` as valid
    var isValidKey = function(k) {