code: function keyUnion(a, b) {
  
      var k = {};
      for (var i in a) {
        k[i] = 1;
      }
      for (var i in b) {
        k[i] = 1;
      }
      return k;
    }
docs: Combines the keys of two objects
  
  @param {Object} a
  @param {Object} b
  @returns {Object}