def dimension_values(self, dimension, expanded=True, flat=True):
        values = []
        found = False
        for el in self:
            if dimension in el.dimensions(label=True):
                values.append(el.dimension_values(dimension))
                found = True
        if not found:
            return super(CompositeOverlay, self).dimension_values(dimension, expanded, flat)
        values = [v for v in values if v is not None and len(v)]
        if not values:
            return np.array()
        vals = np.concatenate(values)
        return vals if expanded else unique_array(vals)
dataset/ETHPy150Open ioam/holoviews/holoviews/core/overlay.py/CompositeOverlay.dimension_values/original