def push(new_scope = {})
      @scopes.unshift(new_scope)
      raise StackLevelError, "Nesting too deep".freeze if @scopes.length > Block::MAX_DEPTH
    end
def push(new_scope = {})
      @scopes.unshift(new_scope)
      raise StackLevelError, "Nesting too deep".freeze if @scopes.length > Block::MAX_DEPTH
    end
Push new local scope on the stack. use <tt>Context#stack</tt> instead