code: function sibling(node, selector, ancestry) {
              var parent = ancestry[0], listProp, keys, i, l, k, m;
              if (!parent) { return false; }
              keys = estraverse.VisitorKeys[parent.type];
              for (i = 0, l = keys.length; i < l; ++i) {
                  listProp = parent[keys[i]];
                  if (isArray(listProp)) {
                      for (k = 0, m = listProp.length; k < m; ++k) {
                          if (listProp[k] !== node && matches(listProp[k], selector, ancestry)) {
                              return true;
                          }
                      }
                  }
              }
              return false;
          }
docs: /*
  Determines if the given node has a sibling that matches the given selector.