How to use the @ethersproject/abstract-provider.Provider.isProvider function in @ethersproject/abstract-provider

constructor(addressOrName, contractInterface, signerOrProvider) {
        logger.checkNew(new.target, Contract);
        // @TODO: Maybe still check the addressOrName looks like a valid address or name?
        //address = getAddress(address);
        defineReadOnly(this, "interface", getStatic((new.target), "getInterface")(contractInterface));
        if (Signer.isSigner(signerOrProvider)) {
            defineReadOnly(this, "provider", signerOrProvider.provider || null);
            defineReadOnly(this, "signer", signerOrProvider);
        }
        else if (Provider.isProvider(signerOrProvider)) {
            defineReadOnly(this, "provider", signerOrProvider);
            defineReadOnly(this, "signer", null);
        }
        else {
            logger.throwArgumentError("invalid signer or provider", "signerOrProvider", signerOrProvider);
        }
        defineReadOnly(this, "callStatic", {});
        defineReadOnly(this, "estimate", {});
        defineReadOnly(this, "functions", {});
        defineReadOnly(this, "populateTransaction", {});
        defineReadOnly(this, "filters", {});
        {
            const uniqueFilters = {};
            Object.keys(this.interface.events).forEach((eventSignature) => {
                let event = this.interface.events[eventSignature];
                defineReadOnly(this.filters, eventSignature, (...args) => {

else {
            if (SigningKey.isSigningKey(privateKey)) {
                if (privateKey.curve !== "secp256k1") {
                    logger.throwArgumentError("unsupported curve; must be secp256k1", "privateKey", "[REDACTED]");
                }
                defineReadOnly(this, "_signingKey", () => privateKey);
            }
            else {
                const signingKey = new SigningKey(privateKey);
                defineReadOnly(this, "_signingKey", () => signingKey);
            }
            defineReadOnly(this, "_mnemonic", () => null);
            defineReadOnly(this, "path", null);
            defineReadOnly(this, "address", computeAddress(this.publicKey));
        }
        if (provider && !Provider.isProvider(provider)) {
            logger.throwArgumentError("invalid provider", "provider", provider);
        }
        defineReadOnly(this, "provider", provider || null);
    }
    get mnemonic() { return this._mnemonic(); }

} else {
            if (SigningKey.isSigningKey(privateKey)) {
                if (privateKey.curve !== "secp256k1") {
                    logger.throwArgumentError("unsupported curve; must be secp256k1", "privateKey", "[REDACTED]");
                }
                defineReadOnly(this, "_signingKey", () => privateKey);
            } else {
                const signingKey = new SigningKey(privateKey);
                defineReadOnly(this, "_signingKey", () => signingKey);
            }
            defineReadOnly(this, "_mnemonic", (): string => null);
            defineReadOnly(this, "path", null);
            defineReadOnly(this, "address", computeAddress(this.publicKey));
        }

        if (provider && !Provider.isProvider(provider)) {
            logger.throwArgumentError("invalid provider", "provider", provider);
        }

        defineReadOnly(this, "provider", provider || null);
    }

const checkSignerType = (signerOrProvider: Signer | Provider) => {
  if (!signerOrProvider) {
    throw Error('signerOrProvider argument is undefined')
  }
  if (
    !Provider.isProvider(signerOrProvider) &&
    !Signer.isSigner(signerOrProvider)
  ) {
    throw Error('signerOrProvider argument is the wrong type')
  }
}