DeleteAttachment.
        [Preview API] Delete a pull request attachment.
        :param str file_name: The name of the attachment to delete.
        :param str repository_id: The repository ID of the pull request’s target branch.
        :param int pull_request_id: ID of the pull request.
        :param str project: Project ID or project name

def delete_attachment(self, file_name, repository_id, pull_request_id, project=None):
        """DeleteAttachment.
        [Preview API] Delete a pull request attachment.
        :param str file_name: The name of the attachment to delete.
        :param str repository_id: The repository ID of the pull request’s target branch.
        :param int pull_request_id: ID of the pull request.
        :param str project: Project ID or project name
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if file_name is not None:
            route_values['fileName'] = self._serialize.url('file_name', file_name, 'str')
        if repository_id is not None:
            route_values['repositoryId'] = self._serialize.url('repository_id', repository_id, 'str')
        if pull_request_id is not None:
            route_values['pullRequestId'] = self._serialize.url('pull_request_id', pull_request_id, 'int')
        self._send(http_method='DELETE',
                   location_id='965d9361-878b-413b-a494-45d5b5fd8ab7',
                   version='5.1-preview.1',
                   route_values=route_values)