def layer_icon(layer):
    """Helper to get the layer icon.

    :param layer: A layer.
    :type layer: QgsMapLayer

    :returns: The icon for the given layer.
    :rtype: QIcon
    """
    if is_raster_layer(layer):
        return QgsLayerItem.iconRaster()
    elif is_point_layer(layer):
        return QgsLayerItem.iconPoint()
    elif is_line_layer(layer):
        return QgsLayerItem.iconLine()
    elif is_polygon_layer(layer):
        return QgsLayerItem.iconPolygon()
    else:
        return QgsLayerItem.iconDefault()
Helper to get the layer icon.

    :param layer: A layer.
    :type layer: QgsMapLayer

    :returns: The icon for the given layer.
    :rtype: QIcon