input: 
  def generate_html_table_for_top_bestselling_books(genre: str) -> str:
      """
      Generate an HTML table displaying information about the top 10 bestselling books in a specific genre.
  
      >>> generate_html_table_for_top_bestselling_books('Fantasy')
      '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>Book1</td><td>Author1</td><td>Fantasy</td><td>1000</td></tr><tr><td>Book2</td><td>Author2</td><td>Fantasy</td><td>900</td></tr></table>'
      """
      import sqlite3
      conn = sqlite3.connect('books.db')
      c = conn.cursor()
      c.execute(f'''SELECT title, author, genre, sales
                   FROM Books
                   WHERE genre=?
                   ORDER BY sales DESC
                   LIMIT 10''', (genre,))
      results = c.fetchall()
      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>'
      return html
  
output:     conn.close()