AddComment.
        [Preview API] Add a comment on a work item.
        :param :class:`<WorkItemCommentCreateRequest> <azure.devops.v5_1.work_item_tracking_comments.models.WorkItemCommentCreateRequest>` request: Comment create request.
        :param str project: Project ID or project name
        :param int work_item_id: Id of a work item.
        :rtype: :class:`<WorkItemCommentResponse> <azure.devops.v5_1.work-item-tracking-comments.models.WorkItemCommentResponse>`

def add_comment(self, request, project, work_item_id):
        """AddComment.
        [Preview API] Add a comment on a work item.
        :param :class:`<WorkItemCommentCreateRequest> <azure.devops.v5_1.work_item_tracking_comments.models.WorkItemCommentCreateRequest>` request: Comment create request.
        :param str project: Project ID or project name
        :param int work_item_id: Id of a work item.
        :rtype: :class:`<WorkItemCommentResponse> <azure.devops.v5_1.work-item-tracking-comments.models.WorkItemCommentResponse>`
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if work_item_id is not None:
            route_values['workItemId'] = self._serialize.url('work_item_id', work_item_id, 'int')
        content = self._serialize.body(request, 'WorkItemCommentCreateRequest')
        response = self._send(http_method='POST',
                              location_id='608aac0a-32e1-4493-a863-b9cf4566d257',
                              version='5.1-preview.1',
                              route_values=route_values,
                              content=content)
        return self._deserialize('WorkItemCommentResponse', response)