Dear Nest Team,

working with Python 3.8 and Nest 3.2 my goal is, after creating a spatial NodeCollection "neurons", to create a new NodeCollection containing a selection of the node from "neurons".
To achieve this I tried two different approaches:

1. Create a Mask object and use nest.SelectNodesByMask()  
    nodes_in_mask = nest.SelectNodesByMask(neurons, ctr_position, mask_obj)

2. Transform the NodeCollection into a list of node ids, pick 3 random ids, and create a new NodeCollection containing those 3 Nodes
    neurons_list = neurons.tolist()
    for x in range(0, 3):
        center = random.choice(neurons_list)
        node_ids.append(center)
    node_ids.sort()
    new_collection = nest.NodeCollection(node_ids)

But with both approaches I get the same problems that some Information (of the positions) seems to go missing. This shows in different ways.
First the new NodeCollections are no longer spatial (nodes_in_mask.spatial and new_collection.spatial return none).
Second trying to get the node Positions results in an Error:
    nest.GetPosition(nodes_in_mask)
    -> Error #1  nest.lib.hl_api_exceptions.LayerExpected: LayerExpected in SLI function GetPosition_g:
And last, trying to Plot the Layer also results in an Error:
    fig = nest.PlotLayer(nodes_in_mask)
    -> Error #2   TypeError: 'NoneType' object is not subscriptable


I attached a .txt file containing py code showing the problems.


Why do those Problems occur and what can I do to solve them?

Is there a way to create an empty NodeCollection s.t. I can add the wished nodes one by one?

What exactly does the metadata of a Nodecollection represent? Is there a way to set it manually for example to spatial?


Thank you in advance for your Answers,

Miriam