def start_new_paragraph(self):
        """Make sure to create an empty line. This is overridden, if the previous
        text ends with the special marker ''. In that case, nothing is done.
        """
        if self.pieces[-1:] == ['']: # respect special marker
            return
        elif self.pieces == []: # first paragraph, add '\n', override with ''
            self.pieces = ['\n']
        elif self.pieces[-1][-1:] != '\n': # previous line not ended
            self.pieces.extend(['  \n' ,'\n'])
        else: #default
            self.pieces.append('\n')
Make sure to create an empty line. This is overridden, if the previous
        text ends with the special marker ''. In that case, nothing is done.