input: from typing import List
  
  def print_customer_data(names: List[str]) -> None:
      """ This function is designed to print customer data based on the provided list of customer names.
      If a name is found in the customer database, it will print the relevant customer information.
      If the name is not found, it will print a message indicating that the customer data is not available.
  
      >>> print_customer_data(['John Doe', 'Jane Smith'])
      John Doe: Age 34, Member since 2018
      Jane Smith: Customer data not available.
      """
      customer_database = {
          'John Doe': {'Age': 34, 'Member since': 2018},
          'Alice Johnson': {'Age': 29, 'Member since': 2020},
      }
      for name in names:
          if name in customer_database:
              print(f"{name}: {', '.join([f'{key} {value}' for key, value in customer_database[name].items()])}")
          else:
              print(f"{name}: Customer data not available.")
output:     customer_database = {
          'John Doe': {'Age': 34, 'Member since': 2018},
          'Alice Johnson': {'Age': 29, 'Member since': 2020},
      }
      for name in names:
          if name in customer_database:
              print(f"{name}: {', '.join([f'{key} {value}' for key, value in customer_database[name].items()])}")
          else:
              print(f"{name}: Customer data not available.")