code: @Nullable
    protected String locate(String scriptAddress, String name) {
      String canonicalizedPath = canonicalizePath(scriptAddress, name);
  
      String normalizedPath = canonicalizedPath;
      if (ModuleLoader.isAmbiguousIdentifier(canonicalizedPath)) {
        normalizedPath = ModuleLoader.MODULE_SLASH + canonicalizedPath;
      }
  
      // First check to see if the module is known with it's provided path
      if (modulePaths.contains(normalizedPath)) {
        return canonicalizedPath;
      }
  
      // Check for the module beneath each of the module roots
      for (String rootPath : moduleRootPaths) {
        String modulePath = rootPath + normalizedPath;
  
        // Since there might be code that relying on whether the path has a leading slash or not,
        // honor the state it was provided in. In an ideal world this would always be normalized
        // to contain a leading slash.
        if (modulePaths.contains(modulePath)) {
          return canonicalizedPath;
        }
      }
  
      return null;
    }
docs: Locates the module with the given name, but returns null if there is no JS file in the expected
  location.