Open PHDOS file produced by Anaddb and returns :class:`PhdosFile` object.

def open_phdos(self):
        """Open PHDOS file produced by Anaddb and returns :class:`PhdosFile` object."""
        from abipy.dfpt.phonons import PhdosFile
        phdos_path = os.path.join(self.workdir, "run.abo_PHDOS.nc")
        if not phdos_path:
            if self.status == self.S_OK:
                logger.critical("%s reached S_OK but didn't produce a PHBST file in %s" % (self, self.outdir))
            return None

        try:
            return PhdosFile(phdos_path)
        except Exception as exc:
            logger.critical("Exception while reading GSR file at %s:\n%s" % (phdos_path, str(exc)))
            return None