class_docstr: Docker container session
  
  Parameters
  ----------
  base_image_name : str
      Docker image name to use. Empty string means to use default "tlcpack/ci-hexagon"
      base image.
class_docstr_tok: ["Docker","container","session","Parameters","--","--","--","--","--","base_image_name",":","str","Docker","image","name","to","use",".","Empty","string","means","to","use","default","``","tlcpack\/ci-hexagon","''","base","image","."]
docstr: Return env var value from docker container
docstr_tok: ["Return","env","var","value","from","docker","container"]
code: def get_env(self, key: str) -> str:
      """Return env var value from docker container"""
      res: str = self.exec(f"bash -c 'echo \"${key}\"'")
      return res.rstrip(" \n")
  
imports: import os
  import pathlib
  import re
  from typing import List, Union
  import subprocess
  import sys
  import tarfile
  import io
  import numpy
  import tvm
  import tvm.contrib.cc
  from ..._ffi.registry import register_func
label_desc: Use image node_id 7 for calling the ContainerSession obj's underlying member method code with example usage: obj.get_env(key) and returns: res