def get_labels(self, depth=None):
        """
        Returns a list of labels created by this reference.

        Parameters
        ----------
        depth : integer or ``None``
            If not ``None``, defines from how many reference levels to
            retrieve labels from.

        Returns
        -------
        out : list of ``Label``
            List containing the labels in this cell and its references.
        """
        if not isinstance(self.ref_cell, Cell):
            return []
        if self.rotation is not None:
            ct = numpy.cos(self.rotation * numpy.pi / 180.0)
            st = numpy.sin(self.rotation * numpy.pi / 180.0)
            st = numpy.array([-st, st])
        if self.magnification is not None:
            mag = numpy.array([self.magnification, self.magnification])
        if self.origin is not None:
            orgn = numpy.array(self.origin)
        if self.x_reflection:
            xrefl = numpy.array([1, -1], dtype='int')
        cell_labels = self.ref_cell.get_labels(depth=depth)
        labels = []
        for ii in range(self.columns):
            for jj in range(self.rows):
                spc = numpy.array([self.spacing[0] * ii, self.spacing[1] * jj])
                for clbl in cell_labels:
                    lbl = libCopy.deepcopy(clbl)
                    if self.magnification:
                        lbl.position = lbl.position * mag + spc
                    else:
                        lbl.position = lbl.position + spc
                    if self.x_reflection:
                        lbl.position = lbl.position * xrefl
                    if self.rotation is not None:
                        lbl.position = lbl.position * ct + lbl.position[::-1] * st
                    if self.origin is not None:
                        lbl.position = lbl.position + orgn
                    labels.append(lbl)
        return labels
Returns a list of labels created by this reference.

        Parameters
        ----------
        depth : integer or ``None``
            If not ``None``, defines from how many reference levels to
            retrieve labels from.

        Returns
        -------
        out : list of ``Label``
            List containing the labels in this cell and its references.