How to use the @0x/sol-resolver.SpyResolver function in @0x/sol-resolver

private _getPathsToWatch(): string[] {
        const contractNames = this.getContractNamesToCompile();
        const spyResolver = new SpyResolver(this._resolver);
        for (const contractName of contractNames) {
            const contractSource = spyResolver.resolve(contractName);
            // NOTE: We ignore the return value here. We don't want to compute the source tree hash.
            // We just want to call a SpyResolver on each contracts and it's dependencies and
            // this is a convenient way to reuse the existing code that does that.
            // We can then get all the relevant paths from the `spyResolver` below.
            getSourceTreeHash(spyResolver, contractSource.path);
        }
        const pathsToWatch = _.uniq(spyResolver.resolvedContractSources.map(cs => cs.absolutePath));
        return pathsToWatch;
    }
    /**

private async _compileContractsAsync(contractNames: string[], shouldPersist: boolean): Promise {
        // batch input contracts together based on the version of the compiler that they require.
        const versionToInputs: VersionToInputs = {};

        // map contract paths to data about them for later verification and persistence
        const contractPathToData: ContractPathToData = {};

        const solcJSReleases = await getSolcJSReleasesAsync(this._isOfflineMode);
        const resolvedContractSources = [];
        for (const contractName of contractNames) {
            const spyResolver = new SpyResolver(this._resolver);
            const contractSource = spyResolver.resolve(contractName);
            const sourceTreeHashHex = getSourceTreeHash(spyResolver, contractSource.path).toString('hex');
            const contractData = {
                contractName: path.basename(contractName, constants.SOLIDITY_FILE_EXTENSION),
                currentArtifactIfExists: await getContractArtifactIfExistsAsync(this._artifactsDir, contractName),
                sourceTreeHashHex: `0x${sourceTreeHashHex}`,
            };
            if (!this._shouldCompile(contractData)) {
                continue;
            }
            contractPathToData[contractSource.path] = contractData;
            const solcVersion =
                this._solcVersionIfExists === undefined
                    ? semver.maxSatisfying(_.keys(solcJSReleases), parseSolidityVersionRange(contractSource.source))
                    : this._solcVersionIfExists;
            if (solcVersion === null) {