You can find the functions to get the toxicity scores in analysis_utils.py. Please go through the Politeness API documentation about how to use Python to call it. You can use the provided API keys or you can use your own API keys.
Getting the politeness scores is a bit of a task. You first need to run the parser_politeness.py script on your data to get the parse for your sentences. Once the sentences are parsed, save them along with the parses in a file. Then, you need to run the politeness/compute_politeness.py script on these parses. Note that the latter only works with Python 2.