[Test] Integration Tests for lib/input/

[hrishikesh-dahiya]

Description

• check_headers.py
• data_cleanup.py
• ps_table.py

In mbox/

• keyword_clustering.py
• keyword_digest.py
• mbox_hdr.py

In imap/

• connection.py
• header.py

[prasadtalasila]

@tejalwakchoure you can work on the check_header.py module.

[prasadtalasila]

Add a class structure for check_headers.py module.