code: function isRequired(schema) {
      var required = false;
      if (schema[SCHEMAREQUIRED]) {
        try {
          required = schema[SCHEMAREQUIRED];
          if (typeof required != "boolean") {
            throw new ValidationException(
              schema[SCHEMAREQUIRED] + " cast exception."
            );
          }
        } catch (e) {
          throw new ValidationException(
            schema[SCHEMAREQUIRED] + " cast exception."
          );
        }
      }
      return required;
    }
docs: Check if a key is required by schema
  @param  {[type]}  schema [description]
  @return {Boolean}        [description]