(command.CommandList children: [ (C {<set>} {<-ex>}) (C {<source>} {($ Id.VSub_DollarName '$TRAVIS_BUILD_DIR') <'/ci/travis_env_common.sh'>}) (C {<pushd>} {($ Id.VSub_DollarName '$ARROW_JS_DIR')}) (C {<npm>} {<install>}) (C {<popd>}) ] )