The same object in different collections. Which collection contains the selected object in outliner?

How to determine which collection contains the selected object (highlighted in blue) in outliner?

The screenshot shows the outliner diagram.
The Cube object is in two different collections - Collection 1, Collection 2.

Using LMB I can select the Cube in Collection 1 and leave the object unselected in Collection 2.

How to use Python to determine the collection in which this object is selected?

Because obj.users_collection produces both collections. And I only need one.

Thank you in advance for any help.

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