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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 contains(self, key):
 """Checks if the specified item exists. Args: key: the key of the item to lookup. Returns: True if the item exists; False otherwise. Raises: Exception if there was an error requesting information about the item. """

    try:
      self._api.objects_get(self._bucket, key)
    except datalab.utils.RequestException as e:
      if e.status == 404:
        return False
      raise e
    except Exception as e:
      raise e
    return True