re added doc existence check

Author: CodingSamrat

filexdb/collection.py

@@ -369,4 +369,12 @@ def _find_document_by_query(self, query: Mapping) -> JsonArray[Document]:
 
         return JsonArray(result)
 
+    def _doc_is_exists(self, doc_id: str) -> bool:
+        # Iterate over all Documents of Collection
+        for doc in self._collection:
+            if doc["_id_"] == doc_id:
+                return True
+
+        return False
+