input: Write a function to create a command-line application in Python that stores customer data and allows the user to query by customer name. The function should accept a customer name as a command-line argument and print the corresponding customer data. If no customer name is provided, the function should print an error message.
  
  def print_customer_data(name): 
      # Code for searching customer data by customer name and 
      # printing results 
      ...
  
  # Main function for the customer search application
  if __name__=="__main__": 
      # Get command line arguments 
      args = sys.argv 
      
      if len(args) == 2: 
          name = args[1]
          print_customer_data(name) 
      else: 
          print("Invalid arguments, please specify a customer name.")
  
  assert print_customer_data("John Doe")==None # Assuming customer "John Doe" exists in the data
  assert print_customer_data("Jane Smith")==None # Assuming customer "Jane Smith" exists in the data
  assert print_customer_data("NonExistingCustomer")==None # Assuming "NonExistingCustomer" does not exist in the data
  assert print_customer_data("")==None # This should print an error message when run from the command line
  assert print_customer_data(None)==None # This should print an error message when run from the command line
output: def print_customer_data(name): 
      customers = {"John Doe": "Data for John Doe", "Jane Smith": "Data for Jane Smith"}
      if name in customers:
          print(customers[name])
      else:
          print("Customer not found.")