Unexpected results when updating property #99
Description
I am receiving some unexpected results updating a property on a vertex, and wanted to make sure it was not user error.
Here is the output of my python shell
>>> import goblin
>>> import asyncio
>>> from goblin import Goblin
>>>
>>> class Person(goblin.Vertex):
... car = goblin.Property(goblin.String)
...
>>> async def store_element(app, vertex1):
... session = await app.session()
... session.add(vertex1)
... await session.flush()
...
>>> async def close(app):
... await app.close()
...
>>> loop = asyncio.get_event_loop()
>>> app = loop.run_until_complete(Goblin.open(loop, hosts=["localhost"]))
>>> app.register(Person)
>>> p1 = Person()
>>> p1.car = "honda"
>>> loop.run_until_complete(store_element(app, p1))
>>> print(p1.car)
honda
>>> p1.car = "toyota"
>>> loop.run_until_complete(store_element(app, p1))
>>> print(p1.car)
['toyota', 'honda']
>>> loop.run_until_complete(close(app))
>>> loop.close()
Notice that instead of overwriting the element, it is appended like an array. I see this behavior using both the regular Property class and VertexProperty class, in which I would expect the behavior to just overwrite the field value. In the gremlin console the particular vertex ends up having 2 fields named car.
gremlin> g.V().has('car').properties()
==>vp[car->toyota]
==>vp[car->honda]
Is this to be expected? I am using Amazon Neptune with the following packages
aiogremlin==3.2.4
goblin==2.0.0
gremlinpython==3.3.1
My suspicion is that somewhere within this function there is something going wrong when doing either the drop iterator or the add iterator that is causing the issue.