input: Write a function to convert a given SQL statement into a Python Pandas DataFrame. The function should take an SQL statement as a string and a database connection object as input, and return a DataFrame.
  
  assert convert_sql_to_df("SELECT * FROM book;", conn).equals(pd.read_sql_query("SELECT * FROM book;", conn))
output: def convert_sql_to_df(sql_statement, conn):
      return pd.read_sql_query(sql_statement, conn)