def _invert_dict(orig_dict):
    """
    Inverting Python dictionary keys and values: Many to one --> One to many
    Args:
        - orig_dict: Dictionary desired to invert.
            + type: dict
    Return:
        - Inverted dictionary
            + type: dict
    """
    return_dict = {}
    for v, k in orig_dict.items():
        try:
            return_dict[k].append(v)
        except KeyError:
            return_dict[k] = [v]
    return return_dict