in src/core/Node.hack [537:547]
final public function addContextMap(
KeyedContainer<string, mixed> $context,
): this {
if ($this->__isRendered) {
throw new UseAfterRenderException(
Str\format("Can't %s after render", __FUNCTION__),
);
}
$this->context = Dict\merge($this->context, $context);
return $this;
}