import difflib


def compute_unified_diff(old_tokens, new_tokens):
  """Computes the diff between |old_tokens| and |new_tokens|.

  Args:
    old_tokens: Token strings corresponding to the old data.
    new_tokens: Token strings corresponding to the new data.

  Returns:
    The diff, in unified diff format.
  """
  return difflib.unified_diff(old_tokens, new_tokens, n=0, lineterm='')