def _validate_otu_ids_and_tree(counts, otu_ids, tree):
    len_otu_ids = len(otu_ids)
    set_otu_ids = set(otu_ids)
    if len_otu_ids != len(set_otu_ids):
        raise ValueError("``otu_ids`` cannot contain duplicated ids.")

    if len(counts) != len_otu_ids:
        raise ValueError("``otu_ids`` must be the same length as ``counts`` "
                         "vector(s).")

    if len(tree.root().children) == 0:
        raise ValueError("``tree`` must contain more than just a root node.")

    if len(tree.root().children) > 2:
        # this is an imperfect check for whether the tree is rooted or not.
        # can this be improved?
        raise ValueError("``tree`` must be rooted.")

    # all nodes (except the root node) have corresponding branch lengths
    # all tip names in tree are unique
    # all otu_ids correspond to tip names in tree
    branch_lengths = []
    tip_names = []
    for e in tree.traverse():
        if not e.is_root():
            branch_lengths.append(e.length)
        if e.is_tip():
            tip_names.append(e.name)
    set_tip_names = set(tip_names)
    if len(tip_names) != len(set_tip_names):
        raise DuplicateNodeError("All tip names must be unique.")
    if np.array([l is not None for l in branch_lengths]).any():
        raise ValueError("All non-root nodes in ``tree`` must have a branch "
                         "length.")
    missing_tip_names = set_otu_ids - set_tip_names
    if missing_tip_names != set():
        n_missing_tip_names = len(missing_tip_names)
        raise MissingNodeError("All ``otu_ids`` must be present as tip names "
                               "in ``tree``. ``otu_ids`` not corresponding to "
                               "tip names (n=%d): %s" %
                               (n_missing_tip_names,
                                " ".join(missing_tip_names)))
dataset/ETHPy150Open biocore/scikit-bio/skbio/diversity/_util.py/_validate_otu_ids_and_tree/operator `is` -> `is not`