input: Write a python function to detect fraudulent transactions in a list of transactions.
  assert fraud_detection([{'user_id': 1, 'amount': 200, 'merchant_id': 101}, {'user_id': 2, 'amount': 300, 'merchant_id': 102}]) == [{'user_id': 1, 'amount': 200, 'merchant_id': 101}]
  assert fraud_detection([{'user_id': 3, 'amount': 500, 'merchant_id': 103}, {'user_id': 4, 'amount': 100, 'merchant_id': 104}]) == [{'user_id': 3, 'amount': 500, 'merchant_id': 103}]
  assert fraud_detection([{'user_id': 1, 'amount': 50, 'merchant_id': 101}, {'user_id': 2, 'amount': 30, 'merchant_id': 102}]) == []
output: def fraud_detection(transactions):
      threshold = 100  # Assuming the threshold for fraudulent transactions is 100
      fraudulent_transactions = [transaction for transaction in transactions if transaction['amount'] > threshold]
      return fraudulent_transactions