How get all the connected nodes of a starting node using gqlalchemy and Memgraph?

Question

I'm going through the how-to-guide on gqlalchemy and I don't see a way to get all the connected nodes of a starting node. I tried supplying only _start_node_id, but I get GQLAlchemyError: Can't load a relationship without a start_node_id and end_node_id. Here’s part fo my code:

john = UserNode(id="1", username="John").save(db)
lang1 = Language(name="en").save(db)
lang2 = Language(name="fr").save(db)

# want all languages which john speaks
Speaks(_start_node_id=john._id).load(db)

# GQLAlchemyError: Can't load a relationship without a start_node_id and end_node_id

Answer 1

A partial loading is currently not supported when using an OGM. You can try this workaround:

class Nodes:
"""
mimic neomodel's SomeNode.nodes.all(), SomeNode.nodes.get_or_none
"""
def init(self, node_class):
self.node_class = node_class

def all(self):
    root_label = self.node_class.__name__

    q = f'MATCH (n:{root_label}) RETURN n'
    res = db.execute_and_fetch(query=q)
    lst = list(map(lambda ob: ob['n'], res))
    return lst

def get_or_none(self, uid: str):
    q = f'MATCH (n {{uid : "{uid}" }}) RETURN n'
    res = db.execute_and_fetch(query=q)
    lst = list(map(lambda ob: ob['n'], res))
    out = lst[0] if len(lst) else None
    return out
    
class NodeAPI(Node):
"""
- neomodel's obj.save(), obj.nodes.all(), obj.get_or_none(),
- my own materialize function, which overwrites the key with actual data
"""
def save(self):
return db.save_node(self)

@classmethod
def nodes(cls):
    return Nodes(cls)

def materialize(self, base_class=None):
    kw = {}
    for key, _ in self.__fields__.items():
        kw[key] = getattr(self, key)

    import inspect
    if base_class is None:
        immediate_parent_class = inspect.getmro(self.__class__)[1]
        return immediate_parent_class(**kw)
    else:
        return base_class(**kw)

def __str__(self):
    kw = {}
    for key, _ in self.__fields__.items():
        kw[key] = getattr(self, key)

    return f'<{type(self).__name__}, {str(kw)}>'