def split_GL_string(GL_string):
    """splits GL-string into alleles;
    if it becomes too complicated, reduce to POS
    """
    if "|" in GL_string: # pretyping contains phasing
        return [GL_string] # put everything into first field
    else:
        alleles = GL_string.split("+")
        if len(alleles) > 4: # GCN > 4 is probably incorrect
            return ["POS"]
        else:
            return alleles