QGIS Split lines into segments

MULTILINE = 5
LINESTRING = 2


def split_lines():
    layer = iface.activeLayer()
    geometry_type = layer.wkbType()

    if geometry_type not in (MULTILINE, LINESTRING):
        return '\nLayer has no line-geometry.'

    features = layer.selectedFeatures()
    if not features:
        return '\nNo features selected'

    layer.startEditing()
    # get the selected features geometry
    for feature in features:
        if geometry_type == MULTILINE:
            geom = feature.geometry().asMultiPolyline()[0]
        else:
            geom = feature.geometry().asPolyline()
        points = list(geom)
        # create new features
        for start_point, end_point in zip(points, points[1:]):
            new_feat = QgsFeature(layer.fields())
            if geometry_type == MULTILINE:
                new_geom = QgsGeometry.fromMultiPolylineXY([[start_point, end_point]])
            else:
                new_geom =  QgsGeometry.fromPolylineXY([start_point, end_point])
            new_feat.setGeometry(new_geom)
            layer.addFeature(new_feat)
    return 'Done.'


if __name__ == '__console__':
    print(split_lines())