Probably a better example a little further down. This Pex is for internal (rule) use only thus

internal=True

, for those, you almost always want a PEX file that runs in venv mode: https://github.com/pantsbuild/pants/blob/725fd415c29440a6333c0f131f67e0b531fa0497/src/python/pants/backend/python/lint/pylint/rules.py#L166-L175