input: Write a function to create a web application that queries and displays data from three different databases: MySQL, MongoDB, and PostgreSQL, using their respective libraries. The function should establish connections to all three databases, execute predefined queries, fetch the results, and then render these results on a web page using a template. If the function successfully displays the queried data, it should return True; otherwise, it should return False.
  
  assert query_and_display_data()==True
  assert render_page(None)==True
output: 
  def query_and_display_data():
      try:
          # Establish connections to MySQL, MongoDB, and PostgreSQL
          mysql_conn = mysql.connector.connect(host='localhost', user='root', password='password', database='mysql_db')
          mongo_client = pymongo.MongoClient("mongodb://localhost:27017/")
          postgres_conn = psycopg2.connect(host='localhost', database='postgres_db', user='postgres', password='password')
          
          # Execute predefined queries
          mysql_cursor = mysql_conn.cursor()
          mysql_cursor.execute("SELECT * FROM mysql_table")
          mysql_results = mysql_cursor.fetchall()
          
          mongo_db = mongo_client['mongo_db']
          mongo_collection = mongo_db['mongo_collection']
          mongo_results = list(mongo_collection.find())
          
          postgres_cursor = postgres_conn.cursor()
          postgres_cursor.execute("SELECT * FROM postgres_table")
          postgres_results = postgres_cursor.fetchall()
          
          # Close connections
          mysql_cursor.close()
          mysql_conn.close()
          mongo_client.close()
          postgres_cursor.close()
          postgres_conn.close()
          
          # Render results on a web page using a template
          template = """
          <html>
          <head><title>Database Results</title></head>
          <body>
              <h1>MySQL Results</h1>
              <ul>
              {% for result in mysql_results %}
                  <li>{{ result }}</li>
              {% endfor %}
              </ul>
              <h1>MongoDB Results</h1>
              <ul>
              {% for result in mongo_results %}
                  <li>{{ result }}</li>
              {% endfor %}
              </ul>
              <h1>PostgreSQL Results</h1>
              <ul>
              {% for result in postgres_results %}
                  <li>{{ result }}</li>
              {% endfor %}
              </ul>
          </body>
          </html>
          """
          rendered_page = Template(template).render(mysql_results=mysql_results, mongo_results=mongo_results, postgres_results=postgres_results)
          
          # Save or display the rendered page
          with open('results.html', 'w') as f:
              f.write(rendered_page)
          
          return True
      except Exception as e:
          return False
  