apply_bpe.py doubles empty lines about subword-nmt HOT 2 CLOSED

    def process_line(self, line):                                                                                                                                                                                                                                     
        """segment line, dealing with leading and trailing whitespace"""                                                                                                                                                                                              
                                                                                                                                                                                                                                                                      
        out = ""                                                                                                                                                                                                                                                      
                                                                                                                                                                                                                                                                      
        leading_whitespace = len(line)-len(line.lstrip())                                                                                                                                                                                                             
        if leading_whitespace and len(line.lstrip()):                                                                                                                                                                                                                 
            out += line[:leading_whitespace]                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                      
        out += self.segment(line)                                                                                                                                                                                                                                     
                                                                                                                                                                                                                                                                      
        trailing_whitespace = len(line)-len(line.rstrip())                                                                                                                                                                                                            
        if trailing_whitespace:                                                                                                                                                                                                                                       
            out += line[-trailing_whitespace:]                                                                                                                                                                                                                        
                                                                                                                                                                                                                                                                      
        return out