input: Write a function that takes a list of strings and a separator/delimiter as input and returns the concatenation of all the elements with the specified separator/delimiter.
  
  def concatenate_strings(strings, separator):
   return separator.join(strings)
  
  assert concatenate_strings(["Sample","Text","Hello"], "|")=="Sample|Text|Hello"
  assert concatenate_strings(["Python", "is", "great"], "-")=="Python-is-great"
  assert concatenate_strings(["", "", ""], ",")==","
  assert concatenate_strings([], "_")==""
  assert concatenate_strings(["Single"], "*")=="Single"
output: def concatenate_strings(strings, separator):
   return separator.join(strings)