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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 isfile(self, version=None, *args, **kwargs):
        '''
        Check whether the path exists and is a file
        '''
        version = _process_version(self, version)

        path = self.get_version_path(version)
        self.authority.fs.isfile(path, *args, **kwargs)