This is a part of Vim-Elixir-IDE package.

Provides automatic folding of Elixir source files.

• function signature is shown if available
• multiple clause heads folded together

Drop the file in ~/.vim/plugin or ~/vimfiles/plugin folder, or if you use pathogen into the ~/.vim/bundle/vim-elixir-fold or ~/vimfiles/bundle/vim-elixir-fold.