def _post_request(self, url, headers, data=None):
        """
        Issue a POST request to the specified endpoint with the data provided.

        :param url: str
        :pararm headers: dict
        :param data: dict
        """

        # Grab file from data.
        files = None
        for field, value in data:
            if field == 'file':
                if isinstance(value, dict):
                    files = value
                else:
                    files = {'file': value}
                break

        # Remove file entry from data.
        data[:] = [tup for tup in data if tup[0] != 'file']

        return self._session.post(url, headers=headers, data=data, files=files)
Issue a POST request to the specified endpoint with the data provided.

        :param url: str
        :pararm headers: dict
        :param data: dict