chore: update extract() docstring to specify pd.DataFrame

Author: Prince12369

app/etl/extract.py

@@ -3,7 +3,7 @@
 # TODO (Find & Fix)
 from typing import Optional
 
-def extract(path: str = "xyz.csv") -> ________:  # TODO (Find & Fix)
+def extract(path: str = "xyz.csv") -> pd.DataFrame :
     """
     Extracts data from CSV file.