I am not sure what you are up to and the API changes in remote connections may have confused you.

If you want to see the labels of all vertices in the graph (for janusgraph-0.6.x with gremlin_python-3.5.1):

from gremlin_python.process.anonymous_traversal import traversal
g = traversal().withRemote(DriverRemoteConnection('ws://localhost:8182/gremlin','g'))
g.V().label().toList

If you want to see the vertex labels that you defined in the JanusgGraph schema:

from gremlin_python.driver.client import Client
client = Client('ws://localhost:8182/gremlin', 'graph')
for line in client.submit("graph.openManagement().printSchema()").next():
    print(line)

Best wishes,    Marc