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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_user_roles(user):
 """Return a list of all of the user's roles."""

    if not hasattr(user, '_role_cache'):
        user._role_cache = list(TenantRole.objects.filter(user=user).values_list(
            'group', 'role', 'tenant'))
    return user._role_cache