input: from typing import List
  
  
  def isValidTransaction(transaction: dict) -> bool:
      """
      This function checks if the given transaction dictionary meets the basic 
      requirements for a valid transaction in a blockchain system.
      
      The transaction dictionary must contain the following keys:
      - 'sender': A string representing the sender's public key.
      - 'receiver': A string representing the receiver's public key.
      - 'amount': A float representing the transaction amount.
      - 'timestamp': A string representing the timestamp of the transaction in ISO format.
      
      The sender and receiver keys must not be the same, and the amount must be 
      a positive number.
      
      >>> isValidTransaction({'sender': 'Alice', 'receiver': 'Bob', 'amount': 50.0, 'timestamp': '2023-10-01T12:00:00Z'})
      True
      >>> isValidTransaction({'sender': 'Alice', 'receiver': 'Alice', 'amount': 50.0, 'timestamp': '2023-10-01T12:00:00Z'})
      False
      >>> isValidTransaction({'sender': 'Alice', 'receiver': 'Bob', 'amount': -50.0, 'timestamp': '2023-10-01T12:00:00Z'})
      False
      """
output:     required_keys = ['sender', 'receiver', 'amount', 'timestamp']
      if not all(key in transaction for key in required_keys):
          return False
      
      sender = transaction['sender']
      receiver = transaction['receiver']
      amount = transaction['amount']
      
      if sender == receiver:
          return False
      
      if amount <= 0:
          return False
      
      return True