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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 get_authuser_model():
 """ Define and return AuthUser model using nefertari base classes """

    from nefertari.authentication.models import AuthUserMixin
    from nefertari import engine

    class AuthUser(AuthUserMixin, engine.BaseDocument):
        __tablename__ = 'ramses_authuser'

    return AuthUser