def dict_merge(dct, merge_dct):
    """ Recursive dict merge. Inspired by :meth:``dict.update()``, instead of
    updating only top-level keys, dict_merge recurses down into dicts nested
    to an arbitrary depth, updating keys. The ``merge_dct`` is merged into
    ``dct``.
    :param dct: dict onto which the merge is executed
    :param merge_dct: dct merged into dct
    :return: None
    """
    for key in merge_dct.keys():
        if (
            key in dct
            and isinstance(dct[key], dict)
            and isinstance(merge_dct[key], collections.Mapping)
        ):
            dict_merge(dct[key], merge_dct[key])
        else:
            dct[key] = merge_dct[key]