def _check_analyze(self, *e):
        linenum = int(self._textwidget.index('insert').split('.')[0])
        if linenum != self._linenum:
            self._clear_tags(linenum)
            self._analyze_line(self._linenum)
            self._linenum = linenum
Check if we've moved to a new line.  If we have, then remove
dataset/ETHPy150Open nltk/nltk/nltk/draw/cfg.py/CFGEditor._check_analyze