input: Write a function to concatenate a list of strings with a specified separator/delimiter. If the list is empty, return an empty string.
  def concatenate_strings(strings, separator):
   return separator.join(strings) if strings else ""
   
  assert concatenate_strings(["Sample", "Text", "Hello"], " | ") == "Sample | Text | Hello"
  assert concatenate_strings([], " - ") == ""
output: def concatenate_strings(strings, separator):
      return separator.join(strings) if strings else ""