def texts_from_spans(self, spans, sep=' '):
        """Retrieve texts from a list of (start, end) position spans.

        Parameters
        ----------

        sep: str
            Separator for multilayer elements (default: ' ').

        Returns
        -------
        list of str
            List of strings that correspond to given spans.
        """
        text = self.text
        texts = []
        for start, end in spans:
            if isinstance(start, list):
                texts.append(sep.join(text[s:e] for s, e in zip(start, end)))
            else:
                texts.append(text[start:end])
        return texts
Retrieve texts from a list of (start, end) position spans.

        Parameters
        ----------

        sep: str
            Separator for multilayer elements (default: ' ').

        Returns
        -------
        list of str
            List of strings that correspond to given spans.