docs: public final AntlrDatatypeRuleToken ruleOpExponent() throws RecognitionException {
          AntlrDatatypeRuleToken current = new AntlrDatatypeRuleToken();
  
          Token kw=null;
  
  
          	enterRule();
  
          try {
              // InternalSARL.g:8964:2: (kw= '**' )
              // InternalSARL.g:8965:2: kw= '**'
              {
              kw=(Token)match(input,72,FOLLOW_2); if (state.failed) return current;
              if ( state.backtracking==0 ) {
  
                		current.merge(kw);
                		newLeafNode(kw, grammarAccess.getOpExponentAccess().getAsteriskAsteriskKeyword());
                	
              }
  
              }
  
              if ( state.backtracking==0 ) {
  
                	leaveRule();
  
              }
          }
  
              catch (RecognitionException re) {
                  recover(input,re);
                  appendSkippedTokens();
              }
          finally {
          }
          return current;
      }