input: from typing import List
  
  def generate_html_table(genre: str, books: List[tuple]) -> str:
      """ Generate an HTML table displaying the top 10 bestselling books in a specific genre.
      >>> generate_html_table('Fantasy', [(1, 'Book1', 'Author1', 'Fantasy', 100), (2, 'Book2', 'Author2', 'Fantasy', 90)])
      '<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>100</td></tr><tr><td>Book2</td><td>Author2</td><td>Fantasy</td><td>90</td></tr></table>'
      """
output:     html = '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>'
      for rank, title, author, book_genre, sales in books:
          if book_genre == genre:
              html += f'<tr><td>{title}</td><td>{author}</td><td>{genre}</td><td>{sales}</td></tr>'
      html += '</table>'
      return html