code: function findFile (schema, url) {
    if (schema.files.length === 0) {
      return null;
    }
  
    if (url instanceof File) {
      // Short-circuit behavior for File obejcts
      return findByURL(schema.files, url.url);
    }
  
    // Try to find an exact URL match
    var file = findByURL(schema.files, url);
  
    if (!file) {
      // Resolve the URL and see if we can find a match
      var absoluteURL = schema.plugins.resolveURL({ from: schema.rootURL, to: url });
      file = findByURL(schema.files, absoluteURL);
    }
  
    return file;
  }
docs: Finds the given file in the schema
  
  @param {Schema} schema
  @param {string|File} url
  An absolute URL, or a relative URL (relative to the schema's root file), or a {@link File} object
  
  @returns {?File}