'Returns the attachment that has the specified ID. Attachment
IDs are generated by the case management system when you add
an attachment to a case or case communication. Attachment IDs
are returned in the AttachmentDetails objects that are
returned by the DescribeCommunications operation.
:type attachment_id: string
:param attachment_id: The ID of the attachment to return. Attachment
IDs are returned by the DescribeCommunications operation.'

def describe_attachment(self, attachment_id):

    params = {'attachmentId': attachment_id}
    return self.make_request(action='DescribeAttachment', body=json.dumps(params))
