function validateSchema(schema, throwOrLogError) {
  var $schema = schema.$schema;
  if ($schema !== undefined && typeof $schema != 'string')
    throw new Error('$schema must be a string');
  $schema = $schema || this._opts.defaultMeta || defaultMeta(this);
  if (!$schema) {
    this.logger.warn('meta-schema not available');
    this.errors = null;
    return true;
  }
  var valid = this.validate($schema, schema);
  if (!valid && throwOrLogError) {
    var message = 'schema is invalid: ' + this.errorsText();
    if (this._opts.validateSchema == 'log') this.logger.error(message);
    else throw new Error(message);
  }
  return valid;
}
Validate schema
@this   Ajv
@param {Object} schema schema to validate
@param {Boolean} throwOrLogError pass true to throw (or log) an error if invalid
@return {Boolean} true if schema is valid