I try to figure out why my snippet cannot be dropped inside other elements although the code is the same as any regular odoo built-in snippet. Yet it seems that the class on the snippet defines its target.

for example.  s_website_form decides that this snippet can be dropped inside other elements. but why? Where is that behavior defined so I can reproduce it for my own snippet?

section class="s_website_form pt16 pb16 oe_snippet_body" data-vcss="001" data-snippet="s_website_form" data-name="Form">

How can I define my own droppable targets?