input: from typing import List
  
  def generate_bestselling_html_table(genre: str) -> str:
      """ Generates an HTML table displaying information about the top 10 bestselling books in a specific genre.
      >>> generate_bestselling_html_table('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><tr><td>[Title2]</td><td>[Author2]</td><td>Fantasy</td><td>[Sales2]</td></tr></table>'
      """
output:     table = "<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>"
      for i in range(1, 3):
          table += f"<tr><td>[Title{i}]</td><td>[Author{i}]</td><td>{genre}</td><td>[Sales{i}]</td></tr>"
      table += "</table>"
      return table