def index_containing_substring(list_str, substring):
    """For a given list of strings finds the index of the element that contains the
    substring.

    Parameters
    ----------

    list_str: list of strings
    substring: substring

    Returns
    -------

    index: containing the substring or -1

    """
    for i, s in enumerate(list_str):
        if substring in s:
            return i
    return -1