def characters(self, ch):
        """
        Called when we receive some characters.  CDATA characters get passed
        through as is.

        @type ch: C{string}
        """
        if self.inCDATA:
            self.stack[-1].append(ch)
            return
        self.current.append(ch)

        Called when we receive some characters.  CDATA characters get passed
        through as is.

        @type ch: C{string}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/template.py