Function is_arguments 

pub fn is_arguments(v: &Value) -> bool

The bare brand name behind Object.prototype.toString (Array, Uint8Array …), without the [object …] wrapper. Split out so the brand and the Symbol.toStringTag property read cannot disagree about what a value is. Whether v is a function’s arguments object.

Backed by an Array so indices, length, spread and for-of all work, but marked so it does not pass for one: node’s is an exotic, and isArray, the brand and util.types.isArgumentsObject all have to tell them apart.