add write_file and run_python_file with tests

functions/write_file.py

@@ -0,0 +1,18 @@
+import os
+
+def write_file(working_directory, file_path, content):
+    abs_path = os.path.abspath(working_directory)
+    new_file_path = os.path.normpath(os.path.join(abs_path, file_path))
+    valid_target_file = os.path.commonpath([abs_path, new_file_path]) == abs_path
+    if not valid_target_file:
+        return f'Error: Cannot write to "{file_path}" as it is outside the permitted working directory'
+    if os.path.isdir(new_file_path):
+       return f'Error: Cannot write to "{file_path}" as it is a directory'
+    
+    os.makedirs(os.path.dirname(new_file_path), exist_ok=True)
+    try:
+        with open(new_file_path, "w") as f:
+            f.write(content)
+    except Exception as e:
+        return f"Error: {e}"
+    return f'Successfully wrote to "{file_path}" ({len(content)} characters written)'