code: def replace_suffix(to_transform, suffix):
      
      if is_sequence(to_transform):
          transformed = []
          for f in to_transform:
              (base, _) = os.path.splitext(f)
              transformed.append(base + suffix)
          return transformed
      elif is_string(to_transform):
          (base, _) = os.path.splitext(to_transform)
          return base + suffix
      else:
          raise ValueError("replace_suffix takes a single filename as a string or "
                           "a list of filenames to transform.")
docs: replaces the suffix on a filename or list of filenames
      example: replace_suffix("/path/to/test.sam", ".bam") ->
      "/path/to/test.bam"