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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 _is_did(did):
 """Return True if ``did`` is recorded in a local context. ``did``=None is supported and returns False. A DID can be classified with classify_identifier(). """

    return d1_gmn.app.models.IdNamespace.objects.filter(did=did).exists()