Sends a WARN log message. 
      Syntax
         
         
            public 
            void  
            w
            (
            final String 
            tag
            , 
            final String 
            msg
            )
         
      
      Parameters
         
         
            - 
               tag – 
               Used to identify the source of a log message. It usually identifies the class or activity where the log call occurs.
            
 
            - 
               msg – 
               The message you would like to be logged.
            
 
         
       
      Usage
         
         Logger implementation is able to identify the source of the log message at the price of performance penalty. See Logger#w(String,String,String)