input: Write a function that takes a list of strings and a separator/delimiter, and returns the concatenation of all the elements with the specified delimiter.
  def concatenate_strings(strings, separator):
   return separator.join(strings)
  assert concatenate_strings(["Sample", "Text", "Hello"], "-") == "Sample-Text-Hello"
  assert concatenate_strings(["Apple", "Banana", "Orange"], ",") == "Apple,Banana,Orange"
  assert concatenate_strings(["First", "Second"], " ") == "First Second"
  assert concatenate_strings([], "-") == ""
  assert concatenate_strings(["Single"], "-") == "Single"
output: def concatenate_strings(strings, separator):
   return separator.join(strings)