DeletePullRequestReviewer.
        [Preview API] Remove a reviewer from a pull request.
        :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 reviewer_id: ID of the reviewer to remove.
        :param str project: Project ID or project name

def delete_pull_request_reviewer(self, repository_id, pull_request_id, reviewer_id, project=None):
        """DeletePullRequestReviewer.
        [Preview API] Remove a reviewer from a pull request.
        :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 reviewer_id: ID of the reviewer to remove.
        :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 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')
        if reviewer_id is not None:
            route_values['reviewerId'] = self._serialize.url('reviewer_id', reviewer_id, 'str')
        self._send(http_method='DELETE',
                   location_id='4b6702c7-aa35-4b89-9c96-b9abf6d3e540',
                   version='5.1-preview.1',
                   route_values=route_values)