code: function cleanup() {
    const artifacts = ['.requirements'];
    if (this.options.zip) {
      if (this.serverless.service.package.individually) {
        this.targetFuncs.forEach(f => {
          artifacts.push(path.join(f.module, '.requirements.zip'));
          artifacts.push(path.join(f.module, 'unzip_requirements.py'));
        });
      } else {
        artifacts.push('.requirements.zip');
        artifacts.push('unzip_requirements.py');
      }
    }
  
    return BbPromise.all(
      artifacts.map(artifact =>
        fse.removeAsync(path.join(this.servicePath, artifact))
      )
    );
  }
docs: clean up .requirements and .requirements.zip and unzip_requirements.py
  @return {Promise}