code: function operationId(given, method, url, allKnown) {
    var id;
    var generate = given == null;
    if (generate) {
      id = toIdentifier(method + url);
    } else {
      id = toIdentifier(given);
    }
    var duplicated = allKnown.has(id);
    if (duplicated) {
      var i = 1;
      while (allKnown.has(id + '_' + i)) {
        i++;
      }
      id = id + '_' + i;
    }
    if (generate) {
      console.warn(
        "Operation '" +
          method +
          "' on '" +
          url +
          "' defines no operationId. Assuming '" +
          id +
          "'."
      );
    } else if (duplicated) {
      console.warn(
        "Operation '" +
          method +
          "' on '" +
          url +
          "' defines a duplicated operationId: " +
          given +
          '. ' +
          "Assuming '" +
          id +
          "'."
      );
    }
    allKnown.add(id);
    return id;
  }
docs: Returns the actual operation id, assuming the one given.
  If none is given, generates one