"""Utility functions for working with Dict-type structures."""
from typing import MutableMapping


def merge_dicts(dict1, dict2):
    """Recursively merges dict2 into dict1."""
    if not (isinstance(dict1, MutableMapping) and isinstance(dict2, MutableMapping)):
        return dict2

    for k in dict2.keys():
        if dict2[k] is None:
            dict1.pop(k)
        elif k in dict1:
            dict1[k] = merge_dicts(dict1[k], dict2[k])
        else:
            dict1[k] = dict2[k]
    return dict1