Let's model a system where you have areas, and hosts within areas. These are described in a toml file. A host can only be in an area. How can you check that a document following this schema does not have the same hosts in different areas.

For example this is invalid because host2 is in both areas.

[area1]
hosts = ['host1', 'host2']
[area2]
hosts = ['host2','host3']

• Read toml file and convert to internal representation
• Validate internal representation and reject invalid configurations
• Check that hosts are only assigned to a single area
• Report to the user on pass/fail
• Have a -q flag to suppress output
• Return appropriate error codes for use in scripts

• Proper project structure (setuptools)
• Manage any dependencies
• Well defined entry point and CLI
• Should be easily deployable
• Testing
• Logging

• In the provided example I have uncapitalised the "hosts" key as TOML is case-sensitive. I am assuming that a host-area TOML file with a capitalised "hosts" key is invalid.