+# this block implements tha W3C spec
+# # 1. If the current node is an HTML element whose tag name is subject,
+# # then run these substeps:
+# #
+# # 1. Let element be the current node.
+# #
+# # 2. Pop element off the stack of open elements.
+# #
+# # 3. If element is also in the list of active formatting elements,
+# # remove the element from the list.
+# #
+# # 4. Abort the adoption agency algorithm.
+# if open_els[0].name is subject and open_els[0].namespace is NS_HTML
+# el = open_els.shift()
+# # remove it from the list of active formatting elements (if found)
+# for t, i in afe
+# if t is el
+# afe.splice i, 1
+# break
+# debug_log "aaa: starting off with subject on top of stack, exiting"
+# return
+# WHATWG: https://html.spec.whatwg.org/multipage/syntax.html#adoption-agency-algorithm
+ # If the current node is an HTML element whose tag name is subject, and
+ # the current node is not in the list of active formatting elements,
+ # then pop the current node off the stack of open elements, and abort
+ # these steps.