def get_output_ref(self, field, index=None, metadata=None):
        '''
        :param field: Output field name of this analysis
        :type field: string
        :param index: If the referenced field is an array, optionally specify an index (starting from 0) to indicate a particular member of the array
        :type index: int
        :param metadata: If the referenced field is of a data object class, a string indicating the metadata that should be read, e.g. "name", "properties.propkey", "details.refgenome"
        :type metadata: string

        Returns a dict containing a valid reference to an output of this analysis.
        '''

        link = {"$dnanexus_link": {"analysis": self._dxid, "field": field}}
        if index is not None:
            link["$dnanexus_link"]["index"] = index
        if metadata is not None:
            link["$dnanexus_link"]["metadata"] = metadata
        return link