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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 exists(self, filename):
 """Check for the existence of a package or script. Unlike other DistributionPoint types, JDS and CDP types have no documented interface for checking whether the server and its children have a complete copy of a file. The best we can do is check for an object using the API /packages URL--JSS.Package() or /scripts and look for matches on the filename. If this is not enough, please use the alternate exists_with_casper method. For example, it's possible to create a Package object but never upload a package file, and this method will still return "True". Also, this may be slow, as it needs to retrieve the complete list of packages from the server. """

        # Technically, the results of the casper.jxml page list the
        # package files on the server. This is an undocumented
        # interface, however.
        result = False
        if is_package(filename):
            packages = self.connection["jss"].Package().retrieve_all()
            for package in packages:
                if package.findtext("filename") == filename:
                    result = True
                    break
        else:
            scripts = self.connection["jss"].Script().retrieve_all()
            for script in scripts:
                if script.findtext("filename") == filename:
                    result = True
                    break

        return result