code: def _git_version():
      
  
      import subprocess
      import os
  
      def _minimal_ext_cmd(cmd):
          # construct minimal environment
          env = {}
          for k in ['SYSTEMROOT', 'PATH']:
              v = os.environ.get(k)
              if v is not None:
                  env[k] = v
          # LANGUAGE is used on win32
          env['LANGUAGE'] = 'C'
          env['LANG'] = 'C'
          env['LC_ALL'] = 'C'
          FNULL = open(os.devnull, 'w')
          cwd = os.path.dirname(os.path.realpath(__file__))
          proc = subprocess.Popen(
              cmd, stdout=subprocess.PIPE, stderr=FNULL, env=env, cwd=cwd)
          out = proc.communicate()[0]
          return out
  
      try:
          out = _minimal_ext_cmd(['git', 'rev-parse', 'HEAD'])
          return out.strip().decode('ascii')
      except OSError:
          return "unknown"
docs: If installed with 'pip installe -e .' from inside a git repo, the
      current git revision as a string