lib/ContextStackTrait.php
public function popContext()
    {
        list(
            $this->elementMap,
            $this->contextUri,
            $this->namespaceMap,
            $this->classMap
        ) = array_pop($this->contextStack);
    }
public function popContext()
    {
        list(
            $this->elementMap,
            $this->contextUri,
            $this->namespaceMap,
            $this->classMap
        ) = array_pop($this->contextStack);
    }
Restore the previous "context".