input: from typing import List
  
  def generate_html_table(genre: str, books: List[tuple]) -> str:
      """ Generates an HTML table displaying information about the top 10 bestselling books in a specific genre.
      The input is a list of tuples where each tuple contains the title, author, genre, and sales of a book.
      The function returns a string containing the HTML table.
      >>> generate_html_table('Fantasy', [('Harry Potter', 'J.K. Rowling', 'Fantasy', 12000000), ('The Hobbit', 'J.R.R. Tolkien', 'Fantasy', 10000000)])
      "<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>Harry Potter</td><td>J.K. Rowling</td><td>Fantasy</td><td>12000000</td></tr><tr><td>The Hobbit</td><td>J.R.R. Tolkien</td><td>Fantasy</td><td>10000000</td></tr></table>"
      """
output:     html_table = "<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>"
      for book in books:
          title, author, book_genre, sales = book
          if book_genre == genre:
              html_table += f"<tr><td>{title}</td><td>{author}</td><td>{book_genre}</td><td>{sales}</td></tr>"
      html_table += "</table>"
      return html_table