input: 
  def generate_html_table_for_top_books(genre: str) -> str:
      """
      Generate an HTML table displaying information about the top 10 bestselling books in a specific genre.
      The table retrieves data from a SQLite database named 'books.db'.
      >>> generate_html_table_for_top_books('Fantasy')
      '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>[Title1]</td><td>[Author1]</td><td>[Fantasy]</td><td>[Sales1]</td></tr>...</table>'
      """
      import sqlite3
  
      # connect to the database
      conn = sqlite3.connect('books.db')
      c = conn.cursor()
  
      # retrieve the data
      c.execute(f'''SELECT title, author, genre, sales
      FROM Books
      WHERE genre=?
      ORDER BY sales DESC
      LIMIT 10''', (genre,))
  
      # save the results
      results = c.fetchall()
  
      # generate the HTML code
      html = '<table>'
      html += '<tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>'
  
      for result in results:
          title = result[0]
          author = result[1]
          genre = result[2]
          sales = result[3]
  
          html += f'<tr><td>{title}</td><td>{author}</td><td>{genre}</td><td>{sales}</td></tr>'
  
      html += '</table>'
  
      # display the results
      return html
  
output:     # close the database connection
      conn.close()