How to use the @accordproject/ergo-compiler.FileLoader function in @accordproject/ergo-compiler

* distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use strict';

const fs = require('fs');
const fsPath = require('path');
const slash = require('slash');
const JSZip = require('jszip');
const xregexp = require('xregexp');
const languageTagRegex = require('ietf-language-tag-regex');
const DefaultArchiveLoader = require('./loaders/defaultarchiveloader');
const FileLoader = require('@accordproject/ergo-compiler').FileLoader;
const Logger = require('@accordproject/concerto-core').Logger;

// Matches 'sample.md' or 'sample_TAG.md' where TAG is an IETF language tag (BCP 47)
const IETF_REGEXP = languageTagRegex({ exact: false }).toString().slice(1,-2);
const SAMPLE_FILE_REGEXP = xregexp('text[/\\\\]sample(_(' + IETF_REGEXP + '))?.md$');

/**
 * A utility class to create templates from data sources.
 * @class
 * @private
 * @abstract
 */
class TemplateLoader extends FileLoader {
    /**
     * Create a template from an archive.
     * @param {*} Template - the type to construct