def parse(self, limit=None):
        """
        MPD data is delivered in four separate csv files and one xml file,
        which we process iteratively and write out as
        one large graph.

        :param limit:
        :return:
        """
        if limit is not None:
            LOG.info("Only parsing first %s rows fo each file", str(limit))

        LOG.info("Parsing files...")

        self._process_straininfo(limit)
        # the following will provide us the hash-lookups
        # These must be processed in a specific order

        # mapping between assays and ontology terms
        self._process_ontology_mappings_file(limit)
        # this is the metadata about the measurements
        self._process_measurements_file(limit)
        # get all the measurements per strain
        self._process_strainmeans_file(limit)

        # The following will use the hash populated above
        # to lookup the ids when filling in the graph
        self._fill_provenance_graph(limit)

        LOG.info("Finished parsing.")
        return
MPD data is delivered in four separate csv files and one xml file,
        which we process iteratively and write out as
        one large graph.

        :param limit:
        :return: