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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_page_templates():
 """The callable that is used by the CMS."""

    PAGE_TEMPLATES = get_setting('PAGE_TEMPLATES',
        default_value=())
    if isinstance(PAGE_TEMPLATES, collections.Callable):
        return PAGE_TEMPLATES()
    else:
        return PAGE_TEMPLATES