input: from typing import List, Tuple
  
  def select_horror_movies(cursor):
      """Execute an SQL query to select all movies from the 'Movies' table that belong to the 'horror' category.
      
      >>> import sqlite3
      >>> conn = sqlite3.connect('movies.db')
      >>> cursor = conn.cursor()
      >>> query_result = select_horror_movies(cursor)
      >>> conn.close()
      >>> isinstance(query_result, List)
      True
      """
      cursor.execute("SELECT * FROM Movies WHERE category = 'horror'")
      return cursor.fetchall()
output:     cursor.execute("SELECT * FROM Movies WHERE category = 'horror'")
      return cursor.fetchall()