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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 _forwards(apps, schema_editor):
 """ Make sure that the MarkupItem model actually points to the correct proxy model, that implements the given language. """

    # Need to work on the actual models here.
    from fluent_contents.plugins.markup.models import LANGUAGE_MODEL_CLASSES
    from fluent_contents.plugins.markup.models import MarkupItem
    from django.contrib.contenttypes.models import ContentType

    ctype = ContentType.objects.get_for_model(MarkupItem)

    for language, proxy_model in LANGUAGE_MODEL_CLASSES.items():
        proxy_ctype = ContentType.objects.get_for_model(proxy_model, for_concrete_model=False)
        MarkupItem.objects.filter(
            polymorphic_ctype=ctype, language=language
        ).update(
            polymorphic_ctype=proxy_ctype
        )