code: public void fatal( Object messagePattern, Object arg )
      {
          if( m_delegate.isFatalEnabled() )
          {
              String msgStr = (String) messagePattern;
              msgStr = MessageFormatter.format( msgStr, arg );
              m_delegate.fatal( msgStr, null );
          }
      }
docs: Log a message with the <code>FATAL</code> level with message formatting
  done according to the value of <code>messagePattern</code> and
  <code>arg</code> parameters.
  <p>
  This form avoids superflous parameter construction. Whenever possible,
  you should use this form instead of constructing the message parameter
  using string concatenation.
  
  @param messagePattern The message pattern which will be parsed and formatted
  @param arg            The argument to replace the formatting element, i,e,
  the '{}' pair within <code>messagePattern</code>.
  
  @since 1.3