code: def interleaved_filename(file_path):
      
      if not isinstance(file_path, tuple):
          raise OneCodexException("Cannot get the interleaved filename without a tuple.")
      if re.match(".*[._][Rr][12][_.].*", file_path[0]):
          return re.sub("[._][Rr][12]", "", file_path[0])
      else:
          warnings.warn("Paired-end filenames do not match--are you sure they are correct?")
          return file_path[0]
docs: Return filename used to represent a set of paired-end files. Assumes Illumina-style naming
      conventions where each file has _R1_ or _R2_ in its name.