Add is_colab() and is_kaggle() (#41)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/engine/trainer.py

@@ -11,7 +11,6 @@ import time
 from collections import defaultdict
 from datetime import datetime
 from pathlib import Path
-from telnetlib import TLS
 from typing import Dict, Union
 
 import torch

ultralytics/yolo/engine/validator.py

@@ -1,7 +1,7 @@
 import logging
 
 import torch
-from omegaconf import DictConfig, OmegaConf
+from omegaconf import OmegaConf
 from tqdm import tqdm
 
 from ultralytics.yolo.engine.trainer import DEFAULT_CONFIG