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 separator. The function should be named `concatenate_strings`, and it should take two parameters: `strings` and `separator`. If the list is empty, the function should return an empty string.
  assert concatenate_strings(["Sample", "Text", "Hello"], "/") == "Sample/Text/Hello"
  assert concatenate_strings(["A", "B", "C"], "-") == "A-B-C"
  assert concatenate_strings([], ",") == ""
  assert concatenate_strings(["One"], ".") == "One"
  assert concatenate_strings(["Hello", "World"], " ") == "Hello World"
output: def concatenate_strings(strings, separator):
      if not strings:
          return ""
      return separator.join(strings)