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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def cache_path(runas=None, env=None):
    '''
    List path of the NPM cache directory.

    runas
        The user to run NPM with

    env
        Environment variables to set when invoking npm. Uses the same ``env``
        format as the :py:func:`cmd.run <salt.modules.cmdmod.run>` execution
        function.

    CLI Example:

    .. code-block:: bash

        salt '*' npm.cache_path

    '''
    env = env or {}

    if runas:
        uid = salt.utils.user.get_uid(runas)
        if uid:
            env.update({'SUDO_UID': uid, 'SUDO_USER': ''})

    cmd = 'npm config get cache'

    result = __salt__['cmd.run_all'](
        cmd, cwd=None, runas=runas, env=env, python_shell=True, ignore_retcode=True)

    return result.get('stdout') or result.get('stderr')