code: function xmultipleClasses(parents) {
      // A dummy constructor because a class can only extend something constructible
      function ConstructibleProxyTarget() {}
  
      // Replace prototype with a forwarding proxy to parents' prototypes
      ConstructibleProxyTarget.prototype = xmultipleObjects(parents.map(parent => parent.prototype));
  
      // Forward static calls to parents
      const ClassForwardingProxy = xmultipleObjects(parents, ConstructibleProxyTarget);
  
      return ClassForwardingProxy;
  }
docs: Creates a proxy that delegates to multiple other constructor functions and
  their prototypes.
  
  @param {Array<ConstructorFunction>} parents The list of constructor functions
  to delegate to.
  @return {Proxy}