Given GOEA namedtuples, return nts w/P-value in string format.

def get_nts_strpval(self, fmt="{:8.2e}"):
        """Given GOEA namedtuples, return nts w/P-value in string format."""
        objntmgr = MgrNts(self.goea_results)
        dcts = objntmgr.init_dicts()
        # pylint: disable=line-too-long
        pval_flds = set(k for k in self._get_fieldnames(next(iter(self.goea_results))) if k[:2] == 'p_')
        for fld_float in pval_flds:
            fld_str = "s_" + fld_float[2:]
            objntmgr.add_f2str(dcts, fld_float, fld_str, fmt)
        return objntmgr.mknts(dcts)