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, execute the query, and return the result as a Pandas DataFrame.
  
  def sql_to_dataframe(sql_query, conn):
      import pandas as pd
      df = pd.read_sql_query(sql_query, conn)
      return df
  
  assert str(sql_to_dataframe("SELECT * FROM book;", conn).shape) == "(10, 5)"
  assert list(sql_to_dataframe("SELECT title, author FROM book;", conn).columns) == ["title", "author"]
  assert sql_to_dataframe("SELECT * FROM non_existent_table;", conn).empty == True
output: def sql_to_dataframe(sql_query, conn):
      import pandas as pd
      df = pd.read_sql_query(sql_query, conn)
      return df