Create a poc module for utilities that help with proof-of-concept

[npatki]

Problem Description

A few of the newer functions in the utils module are specifically being added to allow users to easily perform a proof-of-concept with a multi-table dataset. It would be nice to group these functions in a sub-module to keep them organized and communicate exactly what these functions are needed for.

Expected behavior

Create a submodule called poc inside of utils. We will expect users to import the poc submodule specifically in order to access the functions.

from utils import poc

valid_data = poc.drop_unknown_references(metadata, data)

The relevant functions inside poc should be:

• drop_unknown_references (Add verbosity to drop_unknown_references #1845)
• simplify_schema (Add utility function to simplify multi-table schemas #1832)
• get_random_subset (to be filed)

Note that these function should not be accessible through utils alone -- only through poc. It is also ok if users want to import these functions alone:

from utils.poc import drop_unknown_references