"Parse Error: Unexpected indent."
"expansion.gd: 2525"
Edit: 2525 is the line number of the error(though any lines you changed will have the same error, only the first one is listed)
The text in the browser has spaces instead of tabs, which will likely upset the Godot engine when copying the text from the browser to the text editor. It believes you are missing tabs/indent cause there are spaces instead. Replace groups of 4 spaces with a tab. Some text editors have this functionality built in, otherwise use the "Find and Replace"/"Replace...".