def too_few_otus(tree, threshold):
    """
    Return true if the provided tree node object have fewer OTUs than the
    provided threshold.

    Parameters
    ----------
    tree : TreeNode object
        The tree you wish to consider.
    threshold : int
        Minimum number of OTUs allowed in the provided tree.

    Returns
    -------
    True or False
        True if the tree contains to few OTUs.
    """
    return len(set(tree.iter_otus())) < threshold
