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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 set_preferences(request, dashboard_id):
 """ This view serves and validates a preferences form. """

    try:
        preferences = DashboardPreferences.objects.get(
            user=request.user,
            dashboard_id=dashboard_id
        )
    except DashboardPreferences.DoesNotExist:
        preferences = None
    if request.method == "POST":
        form = DashboardPreferencesForm(
            user=request.user,
            dashboard_id=dashboard_id,
            data=request.POST,
            instance=preferences
        )
        if form.is_valid():
            preferences = form.save()
            if request.is_ajax():
                return HttpResponse('true')
            messages.success(request, 'Preferences saved')
        elif request.is_ajax():
            return HttpResponse('false')
    else:
        form = DashboardPreferencesForm(
            user=request.user,
            dashboard_id=dashboard_id,
            instance=preferences
        )
    return render_to_response(
        'admin_tools/dashboard/preferences_form.html',
         {'form': form}
    )