ECDSAKeyIdentity from privateKey and publicKey

[honopu]

Describe the solution you'd like
I had use ECDSAKeyIdentity.fromKeyPair,but when i use crypto.subtle.importKey to crypto the privateKey and publicKey, throw Cannot create a key using the specified key usages.

This is the code

await window.crypto.subtle.importKey("raw", privateKey, { name: "ECDSA", namedCurve: "P-256" }, false, ["sign"]);

So ECDSAKeyIdentity could import from privateKey and publicKey? Or how to crypto the privatekey and publicKey?