code: def _do_shell(self, line):
          
          if not line:
              return
          sp = Popen(line,
                     shell=True,
                     stdin=PIPE,
                     stdout=PIPE,
                     stderr=PIPE,
                     close_fds=not WINDOWS)
          (fo, fe) = (sp.stdout, sp.stderr)
          if PY2:
              out = fo.read().strip(EOL)
              err = fe.read().strip(EOL)
          else:
              out = fo.read().decode("utf-8")
              err = fe.read().decode("utf-8")
          if out:
              print(out)
              return
          if err:
              print(err.replace('isbn_', ''))
docs: Send a command to the Unix shell.\n==> Usage: shell ls ~