def plugin_name(plugin)
     tuple = elements.find { |(_, p)| p.equal?(plugin) }
     tuple[0] if tuple
    end
def plugin_name(plugin)
     tuple = elements.find { |(_, p)| p.equal?(plugin) }
     tuple[0] if tuple
    end
Returns plugin name by instance

 @return [Symbol] Plugin name

 @api private