How to use the @polkadot/util-crypto.blake2AsU8a function in @polkadot/util-crypto

function sign (signerPair: IKeyringPair, u8a: Uint8Array): Uint8Array {
  const encoded = u8a.length > 256
    ? blake2AsU8a(u8a)
    : u8a;

  return signerPair.sign(encoded);
}

get hash (): Hash {
    return new Hash(
      blake2AsU8a(this.toU8a(), 256)
    );
  }

public get hash (): IHash {
    return new Raw(this.registry, blake2AsU8a(this.toU8a(), 256));
  }

public get hash (): IHash {
    return new U8a(this.registry, blake2AsU8a(this.toU8a(), 256));
  }

const blake2 = (value: Uint8Array): Uint8Array =>
  blake2AsU8a(value, 512);

public get hash (): IHash {
    return new Raw(this.registry, blake2AsU8a(this.toU8a(), 256));
  }

public get hash (): IHash {
    return createType(this.registry, 'Hash', blake2AsU8a(this.toU8a(), 256));
  }

export function sign (signerPair: IKeyringPair, u8a: Uint8Array, options?: SignOptions): Uint8Array {
  const encoded = u8a.length > 256
    ? blake2AsU8a(u8a)
    : u8a;

  return signerPair.sign(encoded, options);
}

  isBlake2256: (data: HasherInput): Uint8Array => blake2AsU8a(data, 256),
  isTwox128: (data: HasherInput): Uint8Array => xxhashAsU8a(data, 128),