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