Insert multiple documents into the table.

        :param documents: a list of documents to insert
        :returns: a list containing the inserted documents' IDs

def insert_multiple(self, documents):
        """
        Insert multiple documents into the table.

        :param documents: a list of documents to insert
        :returns: a list containing the inserted documents' IDs
        """

        doc_ids = []
        data = self._read()

        for doc in documents:
            doc_id = self._get_doc_id(doc)
            doc_ids.append(doc_id)

            data[doc_id] = dict(doc)

        self._write(data)

        return doc_ids