def find_duplicates(iterable):
    """Find duplicate elements in an iterable.

    Parameters
    ----------
    iterable : iterable
        Iterable to be searched for duplicates (i.e., elements that are
        repeated).

    Returns
    -------
    set
        Repeated elements in `iterable`.

    """
    # modified from qiita.qiita_db.util.find_repeated
    # https://github.com/biocore/qiita
    # see licenses/qiita.txt
    seen, repeated = set(), set()
    for e in iterable:
        if e in seen:
            repeated.add(e)
        else:
            seen.add(e)
    return repeated