Just use it like a normal element. When you need to add or remove a source, send the corresponding http request. The parameters required by these requests are described in detail in the documentation.
source = Gst.ElementFactory.make("nvmultiurisrcbin", "nvmultiurisrcbin")
if not source:
sys.stderr.write(" Unable to create Source \n")
/opt/nvidia/deepstream/deepstream/service-maker/sources/apps/python/pipeline_api/deepstream_test5_app/deepstream_test5.py