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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 retrieve_metadata_server(metadata_key):
 """Retrieve the metadata key in the metadata server. See: https://cloud.google.com/compute/docs/storing-retrieving-metadata :type metadata_key: str :param metadata_key: Key of the metadata which will form the url. You can also supply query parameters after the metadata key. e.g. "tags?alt=json" :rtype: str :returns: The value of the metadata key returned by the metadata server. """

    url = METADATA_URL + metadata_key

    try:
        response = requests.get(url, headers=METADATA_HEADERS)

        if response.status_code == requests.codes.ok:
            return response.text

    except requests.exceptions.RequestException:
        # Ignore the exception, connection failed means the attribute does not
        # exist in the metadata server.
        pass

    return None