Add schema verification step (#955)

* step files, empty notebook

* missing type hint

* fix test

* post review fixes

* fix test and cover new argument

* add copyright

Author: danielperezz

steps/src/.gitkeep

@@ -0,0 +1,20 @@
+apiVersion: v1
+categories:
+  - data-preparation
+  - model-serving
+  - utilities
+description: Verifies the event is aligned with the provided schema
+example: verify_schema.ipynb
+generationDate: 2025-12-29:11-59    
+hidden: false                                       
+labels:
+  author: Iguazio
+mlrunVersion: 1.10.0
+name: verify_schema                        
+className: VerifySchema
+defaultHandler:     
+spec:
+  filename: verify_schema.py              
+  image: mlrun/mlrun                                
+  requirements:
+version: 1.0.0                                      

steps/src/verify_schema/item.yaml

@@ -0,0 +1,66 @@
+# Copyright 2025 Iguazio
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from verify_schema import VerifySchema
+
+class TestVerifySchema:
+    def test_verify_schema(self):
+        schema = ["id", "name", "active"]
+        verifier = VerifySchema(schema=schema, allow_unexpected_keys=False)
+
+        # Test with valid event
+        event = {
+            "id": 1,
+            "name": "Test Event",
+            "active": True
+        }
+        result = verifier.do(event)
+        assert result == event
+
+        # Test with missing key
+        event_missing_key = {
+            "id": 1,
+            "name": "Test Event"
+        }
+        try:
+            verifier.do(event_missing_key)
+        except KeyError as e:
+            assert "missing keys {'active'} in event" in str(e)
+
+        # Test with unexpected key
+        event_unexpected_key = {
+            "id": 1,
+            "name": "Test Event",
+            "active": True,
+            "extra": "unexpected"
+        }
+        try:
+            verifier.do(event_unexpected_key)
+        except KeyError as e:
+            assert "unexpected keys {'extra'} in event" in str(e)
+
+    def test_verify_schema_allow_unexpected(self):
+        schema = ["id", "name", "active"]
+        verifier = VerifySchema(schema=schema, allow_unexpected_keys=True)
+
+        # Test with valid event and unexpected key
+        event = {
+            "id": 1,
+            "name": "Test Event",
+            "active": True,
+            "extra": "unexpected"
+        }
+        result = verifier.do(event)
+        assert result == event

steps/src/verify_schema/test_verify_schema.py

@@ -0,0 +1,33 @@
+{
+ "cells": [
+  {
+   "metadata": {},
+   "cell_type": "code",
+   "outputs": [],
+   "execution_count": null,
+   "source": "",
+   "id": "556b36b9b89d0515"
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 2
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython2",
+   "version": "2.7.6"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

steps/src/verify_schema/verify_schema.ipynb

@@ -0,0 +1,40 @@
+# Copyright 2025 Iguazio
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+class VerifySchema:
+    """
+    This step validates that an event dictionary contains exactly the keys defined in the schema,
+    raising a KeyError if any are missing or unexpected.
+    """
+
+    def __init__(self, schema: list, allow_unexpected_keys: bool = False):
+        self.schema = schema
+        self.allow_unexpected_keys = allow_unexpected_keys
+
+    def do(self, event: dict):
+        # Check if all keys in the expected schema are present in the event
+        missing = set(self.schema) - set(event)
+        if missing:
+            raise KeyError(f"Schema verification failed: missing keys {missing} in event: {event}")
+
+        if self.allow_unexpected_keys:
+            return event
+
+        # Check if there are any unexpected keys in the event
+        unexpected = set(event) - set(self.schema)
+        if unexpected:
+            raise KeyError(f"Schema verification failed: unexpected keys {unexpected} in event: {event}")
+
+        return event