How to search for a __main__ module using pyclbr in Python3?

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-02-18.03:16:48.716>
labels = ['3.8', 'type-bug', 'library']
title = 'How to search for a __main__ module using pyclbr in Python3?'
updated_at = <Date 2021-03-01.22:00:10.867>
user = 'https://github.com/kebab-mai-haddi'

bugs.python.org fields:

activity = <Date 2021-03-01.22:00:10.867>
actor = 'kebab-mai-haddi'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2021-02-18.03:16:48.716>
creator = 'kebab-mai-haddi'
dependencies = []
files = []
hgrepos = []
issue_num = 43247
keywords = []
message_count = 3.0
messages = ['387200', '387524', '387882']
nosy_count = 2.0
nosy_names = ['kxrob', 'kebab-mai-haddi']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue43247'
versions = ['Python 3.8']