input: Write a function to generate an HTML table displaying information about the top 10 bestselling books in a specific genre from a given SQLite database. The function should connect to the database, retrieve the data, and generate the HTML code for the table.
  assert generate_top_books_html_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>100</td></tr><tr><td>Book2</td><td>Author2</td><td>Fantasy</td><td>90</td></tr><!-- Additional rows as per the database content --></table>'
  assert generate_top_books_html_table('Sci-Fi')=='<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr><tr><td>Book5</td><td>Author5</td><td>Sci-Fi</td><td>80</td></tr><tr><td>Book6</td><td>Author6</td><td>Sci-Fi</td><td>70</td></tr><!-- Additional rows as per the database content --></table>'
  assert generate_top_books_html_table('UnknownGenre')==''
  assert generate_top_books_html_table('')==''
output: 
  import sqlite3
  
  def generate_top_books_html_table(genre):
      if not genre:
          return ''
      
      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 ''
      
      html_table = '<table><tr><th>Title</th><th>Author</th><th>Genre</th><th>Sales</th></tr>'
      for row in rows:
          html_table += f'<tr><td>{row[0]}</td><td>{row[1]}</td><td>{row[2]}</td><td>{row[3]}</td></tr>'
      html_table += '</table>'
      
      return html_table
  