def is_mnp(var):
    """
    Determine if the variant is a multi-nucleotide polymorphism
    """
    ref_length = len(var.REF)
    var_length = len(var.ALT[0])
    if ref_length > 0:
        if (ref_length == var_length):
            pass
        else:
            return var
    else:
        return var