private function getPeptideHypothesis(\SimpleXMLElement $xml)
    {
        $hypothesis = array();
        $ref = (string) $xml->attributes()->peptideEvidence_ref;

        $hypothesis['peptide'] = $ref;
        $hypothesis['spectra'] = array();

        // TODO: Nothing we can currently do with this data - yet
        foreach ($xml->SpectrumIdentificationItemRef as $spectrumIdentificationItemRef) {
            $hypothesis['spectra'][] = $this->getSpectrumIdentificationItemRef($spectrumIdentificationItemRef);
        }

        return $hypothesis;
    }