input: Write a function that takes a list of strings and a separator and returns the concatenation of all the elements with the given separator. If the list is empty, the function should 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(["Hello", "World"], ", ")== "Hello, World"
  assert concatenate_strings([], "-")==""
  assert concatenate_strings(["SingleElement"], "|")=="SingleElement"
output: def concatenate_strings(strings, separator):
      return separator.join(strings) if strings else ""