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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 validate(filename=None, ocrd_page=None, ocrd_file=None, strictness='strict', strategy='index1'):
 """ Validates a PAGE file for consistency by filename, OcrdFile or passing OcrdPage directly. Arguments: filename (string):
 Path to PAGE ocrd_page (OcrdPage):
 OcrdPage instance ocrd_file (OcrdFile):
 OcrdFile instance wrapping OcrdPage strictness (string):
 'strict', 'lax', 'fix' or 'off' strategy (string):
 Currently only 'index1' Returns: report (:class:`ValidationReport`) Report on the validity """

        if ocrd_page:
            validator = PageValidator(ocrd_page, strictness, strategy)
        elif ocrd_file:
            validator = PageValidator(page_from_file(ocrd_file), strictness, strategy)
        elif filename:
            validator = PageValidator(parse(filename, silence=True), strictness, strategy)
        else:
            raise Exception("At least one of ocrd_page, ocrd_file or filename must be set")
        return validator._validate()