Delete all metadata of `symbol`

        Parameters
        ----------
        symbol : `str`
            symbol name to delete

def purge(self, symbol):
        """
        Delete all metadata of `symbol`

        Parameters
        ----------
        symbol : `str`
            symbol name to delete
        """
        logger.warning("Deleting entire metadata history for %r from %r" % (symbol, self._arctic_lib.get_name()))
        self.delete_many({'symbol': symbol})