def get_legal_topic_name(topic: str) -> str:
    """Returns a legal Kafka topic name

    Special characters are not allowed in the name
    of a Kafka topic. This method returns a legal name
    after removing special characters and converting each
    letter to lowercase

    Parameters
    ----------
    topic: str
        topic name, essentially an alert parameter which is to be used
        to create a topic

    Returns
    ----------
    legal_topic: str
        A topic name that can be used as a Kafka topic

    Examples
    ----------
    >>> bad_name = 'IaMEvi\\l'
    >>> good_name = get_legal_topic_name(bad_name)
    >>> print(good_name)
    iamevil
    """
    legal_topic = ''.join(a.lower() for a in topic if a.isalpha())
    return legal_topic