code: function() {
                  var a, attachment,
                      e, elements = [],
                      f, filters = new tree.Filterset(),
                      z, zooms = [],
                      segments = 0, conditions = 0;
  
                  while (
                          (e = $(this.element)) ||
                          (z = $(this.zoom)) ||
                          (f = $(this.filter)) ||
                          (a = $(this.attachment))
                      ) {
                      segments++;
                      if (e) {
                          elements.push(e);
                      } else if (z) {
                          zooms.push(z);
                          conditions++;
                      } else if (f) {
                          var err = filters.add(f);
                          if (err) {
                              util.error(env, {
                                  message: err,
                                  index: i - 1,
                                  filename: env.filename
                              });
                              throw new Error('N/A');
                          }
                          conditions++;
                      } else if (attachment) {
                          util.error(env, {
                              message: 'Encountered second attachment name.\n',
                              index: i - 1,
                              filename: env.filename
                          });
                          throw new Error('N/A');
                      } else {
                          attachment = a;
                      }
  
                      var c = input.charAt(i);
                      if (c === '{' || c === '}' || c === ';' || c === ',') { break; }
                  }
  
                  if (segments) {
                      return new tree.Selector(filters, zooms, elements, attachment, conditions, memo);
                  }
              }
docs: Selectors are made out of one or more Elements, see above.