input: Write a function to convert a given SQL statement into a Python Pandas DataFrame. The function should take a SQL query string and a database connection object as input and return a Pandas DataFrame.
  assert convert_sql_to_df("SELECT * FROM book;", conn).equals(pd.read_sql_query("SELECT * FROM book;", conn))==True
  assert convert_sql_to_df("SELECT title, author FROM book;", conn).equals(pd.read_sql_query("SELECT title, author FROM book;", conn))==True
  assert convert_sql_to_df("SELECT year, title FROM book WHERE author='J.K. Rowling';", conn).equals(pd.read_sql_query("SELECT year, title FROM book WHERE author='J.K. Rowling';", conn))==True
  assert convert_sql_to_df("SELECT * FROM book ORDER BY year DESC;", conn).equals(pd.read_sql_query("SELECT * FROM book ORDER BY year DESC;", conn))==True
  assert convert_sql_to_df("SELECT * FROM book LIMIT 5;", conn).equals(pd.read_sql_query("SELECT * FROM book LIMIT 5;", conn))==True
output: def convert_sql_to_df(sql_query, conn):
      return pd.read_sql_query(sql_query, conn)