Adding FileUpload control and updated related components

src/myfasthtml/core/instances.py

@@ -38,6 +38,7 @@ class BaseInstance:
   def get_parent(self):
     return self._parent
 
+
 class SingleInstance(BaseInstance):
   """
   Base class for instances that can only have one instance at a time.
@@ -107,7 +108,11 @@ class InstancesManager:
       if instance_type:
         if not issubclass(instance_type, SingleInstance):
           assert parent is not None, "Parent instance must be provided if not SingleInstance"
-        return instance_type(session, parent=parent, *args, **kwargs)  # it will be automatically registered
+          
+        if isinstance(parent, MultipleInstance):
+          return instance_type(parent, _id=instance_id, *args, **kwargs)
+        else:
+          return instance_type(session, parent=parent, *args, **kwargs)  # it will be automatically registered
       else:
         raise