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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_directory(self, identifier):
 """Implements the policy for naming directories for image objects. Image object directories are name by their identifier. In addition, these directories are grouped in parent directories named by the first two characters of the identifier. The aim is to avoid having too many sub-folders in a single directory. Parameters identifier : string Unique object identifier Returns ------- string Path to image objects data directory """

        return os.path.join(
            os.path.join(self.directory, identifier[:2]),
            identifier
        )