input: Write a function to convert a given SQL statement into a Python Pandas DataFrame. The function should accept the SQL statement as a string and the database connection object as parameters. It should return the resulting DataFrame.
  
  assert convert_sql_to_df("SELECT * FROM book;", conn).equals(pd.read_sql_query("SELECT * FROM book;", conn))
  assert convert_sql_to_df("SELECT title, author FROM book;", conn).equals(pd.read_sql_query("SELECT title, author FROM book;", conn))
  assert convert_sql_to_df("SELECT title FROM book WHERE genre='Science Fiction';", conn).equals(pd.read_sql_query("SELECT title FROM book WHERE genre='Science Fiction';", conn))
  assert convert_sql_to_df("SELECT * FROM none;", conn) is None
output: def convert_sql_to_df(sql_statement, conn):
      try:
          return pd.read_sql_query(sql_statement, conn)
      except:
          return None