2.80: What is socket.socket_id ?

Created by: portnov

On 2.80, one of the tests is failing with the following message:

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ERROR: test_intersect_edges (intersect_edges_tests.IntersectEdgesTest2)
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Traceback (most recent call last):
  File "/home/portnov/.config/blender/2.80/scripts/addons_contrib/sverchok/tests/intersect_edges_tests.py", line 16, in test_intersect_edges
    result_verts = get_output_socket_data(node, "Verts_out")
  File "/home/portnov/.config/blender/2.80/scripts/addons_contrib/sverchok/core/socket_data.py", line 150, in get_output_socket_data
    socket_id = socket.socket_id
AttributeError: 'NodeSocket' object has no attribute 'socket_id'

I was not able to find out what socket.socket_id is supposed to be; it is not mentioned in bpy documentation. Maybe it was some undocumented property that was removed from 2.8? Or was it somehow set by sverchok? I could not find any assignments to this property in our code.