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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 getAttachment(self, oid, attachment_id, out_folder=None):
 """ downloads a feature's attachment. Inputs: oid - object id of the feature attachment_id - ID of the attachment. Should be an integer. out_folder - save path of the file Output: string - full path of the file """

        attachments = self.listAttachments(oid=oid)
        if "attachmentInfos" in attachments:
            for attachment in attachments['attachmentInfos']:
                if "id" in attachment and \
                   attachment['id'] == attachment_id:
                    url = self._url + "/%s/attachments/%s" % (oid, attachment_id)
                    return self._get(url=url, param_dict={"f":'json'},
                                     securityHandler=self._securityHandler,
                                     out_folder=out_folder,
                                     file_name=attachment['name'])
        return None