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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _plain_or_callable(obj):
 """Returns the value of the called object of obj is a callable, otherwise the plain object. Returns None if obj is None. 'select * from sys.nodes' [1, 'name'] 0 [[1, 'foo'], [2, 'bar'], [3, 'foobar']] """

    if callable(obj):
        return obj()
    elif isinstance(obj, types.GeneratorType):
        return next(obj)
    else:
        return obj