setSuperClass(superClass, relatedExpressions) {
    this.superClass = superClass;
    for (const {parent, node} of relatedExpressions) {
      this.replacements.push({
        parent,
        node,
        replacements: []
      });
    }

    this.constructor.setSuperClass(superClass);
  }
Set the superClass and set up the related assignment expressions to be
removed during transformation.
@param {Node} superClass           The super class node.
@param {Node[]} relatedExpressions The related expressions to be removed
                                   during transformation.