Adds union support check when passing in inputs

[skrawcz]

This should fix #170. If an input function was annotated
with a union, we would barf. Now it wont.

This still means downstream nodes need to have the same
type signature -- this doesn't change any behavior there.

Changes

• adds support to expand union type when checking inputs

Testing

1. Unit tests work.

Notes

Checklist

• PR has an informative and human-readable title (this will be pulled into the release notes)
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code passed the pre-commit check & code is left cleaner/nicer than when first encountered.
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future TODOs are captured in comments
• Project documentation has been updated if adding/changing functionality.
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Python - local testing

• python 3.6
• python 3.7

[skrawcz]

This code works

import typing as t
import pandas as pd
def foo_union(x: t.Union[int, pd.Series]) -> t.Union[int, pd.Series]:
    '''foo union'''
    return x + 1
from hamilton.driver import Driver
from hamilton.base import SimplePythonGraphAdapter, DictResult
from hamilton import ad_hoc_utils
lib = ad_hoc_utils.create_temporary_module(foo_union)
initial_columns = {'x': 1}
adapter = SimplePythonGraphAdapter(DictResult)
dr = Driver(initial_columns, lib, adapter=adapter)
print(dr.execute(['foo_union']))

[elijahbenizzy]

OK, I just realized, this is really not the right place to put this. Instead it should live here:

hamilton/hamilton/graph.py

Line 30 in 15271fa

def custom_subclass_check(requested_type: Type[Type], param_type: Type[Type]):

. It doesn't have anything to do with a graph adapter... instead it has to do with forming the DAG. Let's move it over?

[skrawcz]

LGTM - you need to approve @elijahbenizzy