Python 3.9.0a2+ (heads/master:65ecc390c1, Jan 26 2020, 15:39:11) 
[GCC 9.2.1 20191008] on linux
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>>> import ast
>>> source = "(2+2).source"
>>> ast.get_source_segment(source, ast.parse(source).body[0].value)
'2+2).source'
>>> source = "(2+2)[1]"
>>> ast.get_source_segment(source, ast.parse(source).body[0].value)
'2+2)[1]'

I can prepare a patch to extend attribute's col_offset into parens if it is any if approved.