code: def install(args: List[str]) -> None:
      
      with clean_pip_env():
  
          # if being invoked as a pyz, we must ensure we have access to our own
          # site-packages when subprocessing since there is no guarantee that pip
          # will be available
          subprocess_env = os.environ.copy()
          sitedir_index = _first_sitedir_index()
          _extend_python_path(subprocess_env, sys.path[sitedir_index:])
  
          process = subprocess.Popen(
              [sys.executable, "-m", "pip", "--disable-pip-version-check", "install"] + args,
              stdout=subprocess.PIPE,
              stderr=subprocess.STDOUT,
              env=subprocess_env,
          )
  
          for output in process.stdout:
              if output:
                  click.echo(output.decode().rstrip())
  
          if process.wait() > 0:
              sys.exit(PIP_INSTALL_ERROR)
docs: `pip install` as a function.
  
      Accepts a list of pip arguments.
  
      .. code-block:: py
  
          >>> install(['numpy', '--target', 'site-packages'])
          Collecting numpy
          Downloading numpy-1.13.3-cp35-cp35m-manylinux1_x86_64.whl (16.9MB)
              100% || 16.9MB 53kB/s
          Installing collected packages: numpy
          Successfully installed numpy-1.13.3