input: from typing import List
  
  def print_customer_data(names: List[str]):
      """Prints the customer data for each name in the given list of names.
      If a name is not found in the data, it prints a message indicating that.
      If no names are provided, it prints a message asking for customer names.
      
      >>> print_customer_data(["John Doe", "Jane Smith"])
      Customer data for John Doe: ...
      Customer data for Jane Smith: ...
      >>> print_customer_data(["Alice"])
      Customer data for Alice: Not found.
      >>> print_customer_data([])
      Please provide a list of customer names.
      """
output:     if not names:
          print("Please provide a list of customer names.")
          return
      
      customer_data = {
          "John Doe": "...",
          "Jane Smith": "...",
          # Add more customer data as needed
      }
      
      for name in names:
          if name in customer_data:
              print(f"Customer data for {name}: {customer_data[name]}")
          else:
              print(f"Customer data for {name}: Not found.")