/// <summary>
  /// Log a message with the specified <paramref name="logLevel"/>.
  /// </summary>
  /// <param name="logLevel">The level of log entry.</param>
  /// <param name="exception">The exception to log.</param>
  /// <param name="message">The format of the message object to log.<see cref="string.Format(string,object[])"/> </param>
  /// <param name="arg1">The first argument for message formatting.</param>
  [StringFormatMethod("format")]
  void Log<T1>(LogLevel logLevel, [CanBeNull] Exception exception, string message, T1 arg1);