input: Write a function that connects to three different databases (MySQL, MongoDB, and PostgreSQL), executes a query on each, and then renders the results on a web page. Include the necessary import statements for the database libraries and the code to establish connections, execute queries, and close connections. The function should return the data from all three databases to be displayed on the web page. Ensure that the function handles errors if a connection cannot be established or a query fails.
  
  assert render_page('GET') == {'data_mysql': [result from MySQL query], 'data_mongodb': [result from MongoDB query], 'data_postgresql': [result from PostgreSQL query]}
output: def render_page(request):
      import mysql.connector
      from pymongo import MongoClient
      import psycopg2
  
      data = {}
  
      try:
          # MySQL connection and query
          mysql_conn = mysql.connector.connect(host='localhost', user='root', password='password', database='testdb')
          mysql_cursor = mysql_conn.cursor()
          mysql_cursor.execute("SELECT * FROM table_name")
          data['data_mysql'] = mysql_cursor.fetchall()
          mysql_cursor.close()
          mysql_conn.close()
      except Exception as e:
          data['data_mysql'] = str(e)
  
      try:
          # MongoDB connection and query
          mongo_client = MongoClient('localhost', 27017)
          mongo_db = mongo_client['testdb']
          mongo_collection = mongo_db['collection_name']
          data['data_mongodb'] = list(mongo_collection.find())
          mongo_client.close()
      except Exception as e:
          data['data_mongodb'] = str(e)
  
      try:
          # PostgreSQL connection and query
          postgres_conn = psycopg2.connect(host='localhost', database='testdb', user='postgres', password='password')
          postgres_cursor = postgres_conn.cursor()
          postgres_cursor.execute("SELECT * FROM table_name")
          data['data_postgresql'] = postgres_cursor.fetchall()
          postgres_cursor.close()
          postgres_conn.close()
      except Exception as e:
          data['data_postgresql'] = str(e)
  
      return data