input: Write a function to connect to MySQL, MongoDB, and PostgreSQL databases, query data, and display the results on a web page using Python. The function should take no input and should return the rendered webpage with the queried data from all three databases.
  
  
  def display_data_from_databases():
      import pymysql
      from pymongo import MongoClient
      import psycopg2
  
      # connect to MySQL
      connection_mysql = pymysql.connect(host='localhost', user='root', password='password', database='db_name')
  
      # connect to MongoDB
      client = MongoClient('mongodb://localhost:27017')
  
      # connect to PostgreSQL
      connection_postgresql = psycopg2.connect(host='localhost', user='postgres', password='password', dbname='db_name')
  
      # define a query for each database
      query_mysql = 'SELECT * FROM table_name'
      query_mongodb = {'name': 'John Doe'}
      query_postgresql =  'SELECT * FROM table_name WHERE age > 18'
  
      # execute the query and fetch the results
      cursor_mysql = connection_mysql.cursor()
      cursor_mysql.execute(query_mysql)
      result_mysql = cursor_mysql.fetchall()
  
      result_mongodb = client.db_name.collection_name.find(query_mongodb)
  
      cursor_postgresql = connection_postgresql.cursor()
      cursor_postgresql.execute(query_postgresql)
      result_postgresql = cursor_postgresql.fetchall()
  
      # close the connections
      connection_mysql.close()
      client.close() 
      connection_postgresql.close()
  
      # render the results on webpage
      def render_page(request):
          return render(request, 'template.html', {
              'data_mysql': result_mysql, 
              'data_mongodb': result_mongodb,
              'data_postgresql': result_postgresql
          })
  
      return render_page
  
  
  assert display_data_from_databases()('template.html', 'data_mysql', 'data_mongodb', 'data_postgresql')==True
  assert display_data_from_databases()('template.html', 'data_mysql', 'data_mongodb', 'data_postgresql')==True
  assert display_data_from_databases()('template.html', 'data_mysql', 'data_mongodb', 'data_postgresql')==True
  assert display_data_from_databases()('template.html', 'data_mysql', 'data_mongodb', 'data_postgresql')==True
  assert display_data_from_databases()('template.html', 'data_mysql', 'data_mongodb', 'data_postgresql')==True
output: def display_data_from_databases():
      import pymysql
      from pymongo import MongoClient
      import psycopg2
  
      # connect to MySQL
      connection_mysql = pymysql.connect(host='localhost', user='root', password='password', database='db_name')
  
      # connect to MongoDB
      client = MongoClient('mongodb://localhost:27017')
  
      # connect to PostgreSQL
      connection_postgresql = psycopg2.connect(host='localhost', user='postgres', password='password', dbname='db_name')
  
      # define a query for each database
      query_mysql = 'SELECT * FROM table_name'
      query_mongodb = {'name': 'John Doe'}
      query_postgresql =  'SELECT * FROM table_name WHERE age > 18'
  
      # execute the query and fetch the results
      cursor_mysql = connection_mysql.cursor()
      cursor_mysql.execute(query_mysql)
      result_mysql = cursor_mysql.fetchall()
  
      result_mongodb = client.db_name.collection_name.find(query_mongodb)
  
      cursor_postgresql = connection_postgresql.cursor()
      cursor_postgresql.execute(query_postgresql)
      result_postgresql = cursor_postgresql.fetchall()
  
      # close the connections
      connection_mysql.close()
      client.close() 
      connection_postgresql.close()
  
      # render the results on webpage
      def render_page(request):
          return render(request, 'template.html', {
              'data_mysql': result_mysql, 
              'data_mongodb': result_mongodb,
              'data_postgresql': result_postgresql
          })
  
      return render_page