Function is_rpc_method_not_found 

pub fn is_rpc_method_not_found(error: &TransportError) -> bool

Returns whether an RPC transport error reports JSON-RPC method-not-found.

Some providers encode JSON-RPC errors inside an HTTP error response instead of returning a normal JSON-RPC response. Only the exact -32601 code is treated as method unavailability; authentication, internal, and transport errors must remain visible to callers.