code: function adjacent(node, selector, ancestry) {
              var parent = ancestry[0], listProp, keys, i, l, idx;
              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)) {
                      idx = listProp.indexOf(node);
                      if (idx < 0) { continue; }
                      if (idx > 0 && matches(listProp[idx - 1], selector, ancestry)) {
                          return true;
                      }
                      if (idx < listProp.length - 1 && matches(listProp[idx + 1], selector, ancestry)) {
                          return true;
                      }
                  }
              }
              return false;
          }
docs: /*
  Determines if the given node has an asjacent sibling that matches the given selector.