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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 content_id(self, value):
 """The content id for the attachment. This is used when the disposition is set to "inline" and the attachment is an image, allowing the file to be displayed within the email body. :param content_id: The content id for the attachment. This is used when the Disposition is set to "inline" and the attachment is an image, allowing the file to be displayed within the email body. :type content_id: ContentId, string, optional """

        if isinstance(value, ContentId):
            self._content_id = value
        else:
            self._content_id = ContentId(value)