def get_novel_smiles(new_unique_smiles, reference_unique_smiles):
    """Get novel smiles which do not appear in the reference set.

    Parameters
    ----------
    new_unique_smiles : list of str
        List of SMILES from which we want to identify novel ones
    reference_unique_smiles : list of str
        List of reference SMILES that we already have
    """
    return set(new_unique_smiles).difference(set(reference_unique_smiles))