input: Write a function to convert a given SQL statement into a Python Pandas DataFrame. The function should take as input a SQL query string and a database connection object, execute the query, and return the resulting DataFrame.
  
  def sql_to_dataframe(query: str, conn) -> pd.DataFrame:
      import pandas as pd
      return pd.read_sql_query(query, conn)
  
  assert sql_to_dataframe("SELECT * FROM book;", conn).empty == False
  assert sql_to_dataframe("SELECT * FROM book where id = 100;", conn).empty == True
  assert sql_to_dataframe("SELECT * FROM book where price > 100;", conn).empty == True
  assert sql_to_dataframe("SELECT * FROM book where author = 'John Smith';", conn).empty == False
  assert sql_to_dataframe("SELECT * FROM book where year = 2020;", conn).empty == False
output: def sql_to_dataframe(query: str, conn) -> pd.DataFrame:
      import pandas as pd
      return pd.read_sql_query(query, conn)