do not perform_io_checks when reevaluating on field assignment

bioimageio/spec/model/v0_4.py

@@ -57,6 +57,7 @@
 from .._internal.types import LicenseId as LicenseId
 from .._internal.types import NotEmpty as NotEmpty
 from .._internal.url import HttpUrl as HttpUrl
+from .._internal.validation_context import validation_context_var
 from .._internal.validator_annotations import AfterValidator, RestrictCharacters
 from .._internal.version_type import Version as Version
 from .._internal.warning_levels import ALERT, INFO
@@ -875,7 +876,7 @@ class LinkedModel(Node):
 
 
 def package_weights(
-    value: Node,
+    value: Node,  # Union[v0_4.WeightsDescr, v0_5.WeightsDescr]
     handler: SerializerFunctionWrapHandler,
     info: SerializationInfo,
 ):
@@ -891,14 +892,11 @@ def package_weights(
                 + f" ({ctxt.weights_priority_order}) is present in the given model."
             )
 
-        # remove links to parent entry (otherwise we cannot remove the parent)
-        for _, w in value:
-            if w is not None:
-                w.parent = None
-
-        for field_name in value.model_fields:
-            if field_name != wf:
-                setattr(value, field_name, None)
+        # create WeightsDescr with single weight format entry
+        with validation_context_var.get().replace(perform_io_checks=False):
+            new_w = w.model_copy()
+            new_w.parent = None
+            value = value.__class__(**{wf: new_w})
 
     return handler(
         value, info  # pyright: ignore[reportArgumentType]  # taken from pydantic docs