Better way to do the attachments fix

src/Notebook_Processor/notebook_models/notebook_cell_model.py

@@ -6,6 +6,7 @@ from typing import (
     Annotated,
     Union,
     Literal,
+    Optional,
     Any,
 )
 from uuid import uuid4
@@ -17,6 +18,7 @@ from pydantic import (
     field_validator,
     ValidationInfo,
     ConfigDict,
+    model_serializer,
 )
 
 from ..configuration import (
@@ -78,13 +80,35 @@ class BaseNotebookCellModel(BaseModel):
             raise PydanticUseDefault()
         return value
 
+    @model_serializer
+    def drop_optional_none_fields(self):
+        """
+        Drops optional fields that are None.
+
+        We should look for a more dynamic solution to this.
+        Currently those fields need to be hardcoded because there is no way to specifically
+        detect fields that are annotated as Optional because the matching only returns true
+        if you get it exactly (Optional != Optional[dict]).
+
+        :return: The model with the optional fields that are None removed.
+        """
+        optional_fields = [
+            "attachments",
+            ]
+        drop = {key for key, value in self.__dict__.items() if value is None and key in optional_fields}
+        return {
+            key: value
+            for key, value in self.__dict__.items()
+            if key not in drop
+            }
+
 
 class NotebookMarkdownCellModel(BaseNotebookCellModel):
     """
     "Notebook markdown cell."
     """
     cell_type: Literal["markdown"]
-    attachments: dict = Field(default={}, description="Media attachments (e.g. inline images), stored as mimebundle keyed by filename.")
+    attachments: Optional[dict] = Field(default=None, description="Media attachments (e.g. inline images), stored as mimebundle keyed by filename.")
 
 
 class NotebookCodeCellModel(BaseNotebookCellModel):
@@ -101,7 +125,7 @@ class NotebookRawCellModel(BaseNotebookCellModel):
     "Notebook raw nbconvert cell."
     """
     cell_type: Literal["raw"]
-    attachments: dict = Field(default={}, description="Media attachments (e.g. inline images), stored as mimebundle keyed by filename.")
+    attachments: Optional[dict] = Field(default=None, description="Media attachments (e.g. inline images), stored as mimebundle keyed by filename.")
 
 
 NotebookCellAnnotation = Annotated[