Fetch the requested instance metadata entry.
        :param attribute_uri: attribute_uri: attribute name relative to the
        computeMetadata/v1 prefix
        :return:  The value read from the metadata service or None

def get_attribute(attribute_uri):
        """
        Fetch the requested instance metadata entry.
        :param attribute_uri: attribute_uri: attribute name relative to the
        computeMetadata/v1 prefix
        :return:  The value read from the metadata service or None
        """
        attribute_value = get_request(_GCP_METADATA_URI + attribute_uri,
                                      _GCP_METADATA_URI_HEADER)

        if attribute_value is not None and isinstance(attribute_value, bytes):
            # At least in python3, bytes are are returned from
            # urllib (although the response is text), convert
            # to a normal string:
            attribute_value = attribute_value.decode('utf-8')

        transformation = _ATTRIBUTE_URI_TRANSFORMATIONS.get(attribute_uri)
        if transformation is not None:
            attribute_value = transformation(attribute_value)

        return attribute_value