input: Write a function to generate an HTML table displaying information about the top 10 bestselling books in a specific genre from a given database table. The table should include columns for the book's title, author, genre, and sales. The function should connect to a SQLite database, retrieve the data, and format it into an HTML table. If no books are found in the specified genre, an appropriate message should be returned.
  assert generate_bestselling_books_table('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>100000</td></tr><tr><td>Book2</td><td>Author2</td><td>Fantasy</td><td>90000</td></tr><tr><td>Book3</td><td>Author3</td><td>Fantasy</td><td>80000</td></tr><tr><td>Book4</td><td>Author4</td><td>Fantasy</td><td>70000</td></tr><tr><td>Book5</td><td>Author5</td><td>Fantasy</td><td>60000</td></tr><tr><td>Book6</td><td>Author6</td><td>Fantasy</td><td>50000</td></tr><tr><td>Book7</td><td>Author7</td><td>Fantasy</td><td>40000</td></tr><tr><td>Book8</td><td>Author8</td><td>Fantasy</td><td>30000</td></tr><tr><td>Book9</td><td>Author9</td><td>Fantasy</td><td>20000</td></tr><tr><td>Book10</td><td>Author10</td><td>Fantasy</td><td>10000</td></tr></table>'
  assert generate_bestselling_books_table('Mystery')=='No books found in the Mystery genre.'
  assert generate_bestselling_books_table('Science Fiction')=='<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>SciFi1</td><td>SciFiAuthor1</td><td>Science Fiction</td><td>120000</td></tr><tr><td>SciFi2</td><td>SciFiAuthor2</td><td>Science Fiction</td><td>110000</td>{{</table>'
  assert generate_bestselling_books_table('Romance')==''
  assert generate_bestselling_books_table('Horror')==''
output: 
  import sqlite3
  
  def generate_bestselling_books_table(genre):
      conn = sqlite3.connect('books.db')
      cursor = conn.cursor()
      cursor.execute("SELECT title, author, genre, sales FROM books WHERE genre=? ORDER BY sales DESC LIMIT 10", (genre,))
      rows = cursor.fetchall()
      conn.close()
      
      if not rows:
          return 'No books found in the {} genre.'.format(genre)
      
      html_table = '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>'
      for row in rows:
          html_table += '<tr><td>{}</td><td>{}</td><td>{}</td><td>{}</td></tr>'.format(row[0], row[1], row[2], row[3])
      html_table += '</table>'
      
      return html_table
  