input: Write a python function to iterate through a list of programming languages and return a single string with all languages concatenated, separated by commas.
  assert concatenate_languages(["Python", "C++", "Java", "Javascript", "Ruby"]) == "Python,C++,Java,Javascript,Ruby"
  assert concatenate_languages(["Go", "Swift", "Kotlin"]) == "Go,Swift,Kotlin"
  assert concatenate_languages(["C#", "TypeScript"]) == "C#,TypeScript"
output: def concatenate_languages(languages):
      return ",".join(languages)