Prevent appending twice

nbdev_preview.py

@@ -3,17 +3,34 @@
 from nbdev.quarto import nbdev_docs
 
 monkey_patch_procs = """
+# already_appended_marker
 all_procs = FilterDefaults().procs()
 def new_procs(self):
     procs = [proc for proc in all_procs if proc.__name__ != 'clean_magics']
     return procs
 FilterDefaults.procs = new_procs
 """
 
+def check_appeneded_marker(file_path # Path to nbdev.processors.py file
+                           ) -> bool: # True if we already appended new_procs, False otherwise
+    try:
+        with open(file_path, 'r') as file:
+            lines = file.readlines()
+
+            for line in lines:
+                if 'already_appended_marker' in line:
+                    return True
+            return False
+
+    except FileNotFoundError:
+        print(f"File {file_path} not found!")
+
 if __name__ == '__main__':
     module_file_path = inspect.getfile(FilterDefaults)
-
-    with open(module_file_path, 'a') as f:
-        f.write(monkey_patch_procs)
+
+    # Check if we already appended new_procs
+    if not check_appeneded_marker(module_file_path):
+        with open(module_file_path, 'a') as f:
+            f.write(monkey_patch_procs)
 
     nbdev_docs()