input: Write a function to generate an HTML table displaying information about the top 10 bestselling books in a specific genre from a given SQL database. The function should connect to the database, retrieve the data, and print the HTML table. The SQL table is named 'Books' and the columns are: id (int), title (string), author (string), genre (string), sales (int). If the genre specified is 'Fantasy', the function should order the books by sales in descending order and limit the results to 10 books. If the genre specified is not 'Fantasy', the function should return an empty string.
  
  assert generate_top_bestsellers_html(['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>100</td></tr><tr><td>Book2</td><td>Author2</td><td>Fantasy</td><td>90</td></tr><tr><td>Book3</td><td>Author3</td><td>Fantasy</td><td>80</td></tr><tr><td>Book4</td><td>Author4</td><td>Fantasy</td><td>70</td></tr><tr><td>Book5</td><td>Author5</td><td>Fantasy</td><td>60</td></tr><tr><td>Book6</td><td>Author6</td><td>Fantasy</td><td>50</td></tr><tr><td>Book7</td><td>Author7</td><td>Fantasy</td><td>40</td></tr><tr><td>Book8</td><td>Author8</td><td>Fantasy</td><td>30</td></tr><tr><td>Book9</td><td>Author9</td><td>Fantasy</td><td>20</td></tr><tr><td>Book10</td><td>Author10</td><td>Fantasy</td><td>10</td></tr></table>'
  assert generate_top_bestsellers_html(['Mystery'])==''
  assert generate_top_bestsellers_html(['Sci-Fi'])==''
output: 
  def generate_top_bestsellers_html(genre):
      if genre[0] != 'Fantasy':
          return ''
      
      import sqlite3
      conn = sqlite3.connect('books.db')
      cursor = conn.cursor()
      
      cursor.execute("SELECT title, author, genre, sales FROM Books WHERE genre = 'Fantasy' ORDER BY sales DESC LIMIT 10")
      rows = cursor.fetchall()
      
      conn.close()
      
      if not rows:
          return ''
      
      html = '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>'
      for row in rows:
          html += f'<tr><td>{row[0]}</td><td>{row[1]}</td><td>{row[2]}</td><td>{row[3]}</td></tr>'
      html += '</table>'
      
      return html
  