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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def chain_user_names(users, exclude_user, truncate=35):
 """Tag to return a truncated chain of user names."""

    if not users or not isinstance(exclude_user, get_user_model()):
        return ''
    return truncatechars(
        ', '.join(u'{}'.format(u) for u in users.exclude(pk=exclude_user.pk)),
        truncate)