I am working through tutorial here https://www.pantsbuild.org/docs/create-a-new-goal and (have not got to running the code) i suspect, unless there is magic sauce I am not familiar with, the example has a bug

# project_version/targets.py
from pants.engine.target import COMMON_TARGET_FIELDS, SingleSourceField, Target


class ProjectVersionTarget(Target):
    alias = "version_file"
    core_fields = (*COMMON_TARGET_FIELDS, SingleSourceField)
    help = "A project version target representing the VERSION file."

# project_version/register.py
from typing import Iterable

from pants.engine.target import Target
from project_version.target_types import ProjectVersionTarget   <<< incorrect import ?


def target_types() -> Iterable[type[Target]]:
    return [ProjectVersionTarget]

the import in the register example

from project_version.target_types import ProjectVersionTarget

should be

from project_version.targets import ProjectVersionTarget

Looks like it could be a typo. the "convention" in the main repo is that those types of files live at

xyz/target_types.py

https://github.com/pantsbuild/pants/search?q=target_types