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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 apply_post_filters(instance, html):
 """ Allow post processing functions to change the text. This change is not saved in the original text. :type instance: fluent_contents.models.ContentItem :raise ValidationError: when one of the filters detects a problem. """

    for post_func in appsettings.POST_FILTER_FUNCTIONS:
        html = post_func(instance, html)

    return html