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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(self, project_id):
 """Returns an existing emulator instance for the provided project_id. If an emulator instance doesn't yet exist, it creates one. Args: project_id: project ID Returns: a DatastoreEmulator """

    if project_id in self._emulators:
      return self._emulators[project_id]

    emulator = self.Create(project_id)
    self._emulators[project_id] = emulator
    return emulator