class ActionView::Helpers::FormBuilder

def rich_text_area(method, options = {})

Please refer to the documentation of the base helper for details.

<% end %>
<%= f.rich_text_area :content %>
<%= form_with model: @message do |f| %>

Wraps ActionView::Helpers::FormHelper#rich_text_area for form builders: 
def rich_text_area(method, options = {})
  @template.rich_text_area(@object_name, method, objectify_options(options))
end