def pop
      return unless Thread.current.thread_variable_get(STACK_NAME)
      return unless stack.length > 1
      clear_context
      stack.pop
    end
def pop
      return unless Thread.current.thread_variable_get(STACK_NAME)
      return unless stack.length > 1
      clear_context
      stack.pop
    end
Public: Remove the most recently pushed Hash from the stack of contexts.
 If no contexts have been pushed then no action will be taken. The
 default context cannot be popped off the stack; please use the `clear`
 method if you want to remove all key/value pairs from the context.

 Returns nil or the Hash removed from the stack.