add forward for vq model

src/diffusers/models/vae.py

@@ -535,6 +535,11 @@ class VQModel(ModelMixin, ConfigMixin):
         dec = self.decoder(quant)
         return dec
     
+    def forward(self, x):
+        h = self.encode(x)
+        dec = self.decode(h)
+        return dec
+
 
 class AutoencoderKL(ModelMixin, ConfigMixin):
     def __init__(