cordova-plugin-googlemaps: Error installing the plugin in the `multiple-maps` branch

What is your question, problem or request?

Running:

cordova plugin add https://github.com/mapsplugin/cordova-plugin-googlemaps#multiple_maps --variable API_KEY_FOR_ANDROID="SOMETHING" --variable API_KEY_FOR_IOS="SOMETHING" --save

Results in an error:

Error: Failed to fetch plugin https://github.com/mapsplugin/cordova-plugin-googlemaps#multiple_maps via registry. Probably this is either a connection problem, or plugin spec is incorrect. Check your connection and plugin name/version/URL. Failed to get absolute path to installed module

What version of this plugin do you use? I am not yet using the plugin.

npm --v = 5.3.0

This is different error than https://github.com/mapsplugin/cordova-plugin-googlemaps/issues/1578