input: Write a python function to check if a table exists in an SQLite database.
  assert check_table_exists('people-data.db', 'People')==True
  assert check_table_exists('people-data.db', 'Employees')==False
output: def check_table_exists(db_name, table_name):
      import sqlite3
      conn = sqlite3.connect(db_name)
      cursor = conn.cursor()
      cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name=?", (table_name,))
      result = cursor.fetchone()
      conn.close()
      return result is not None