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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_nickname(userid):
 """Return a Future for a nickname from an account."""

  account = yield get_account(userid)
  if not account:
    nickname = 'Unregistered'
  else:
    nickname = account.nickname or account.email
  raise ndb.Return(nickname)