old_contents: """Various utilities fot sequences manipulation"""
  from pysec.utils import xrange
  
  
  def ioc(seq, shift=1):
      """Return the index of coincidence"""
      match = 0
      seq_len = len(seq)
      for i in xrange(0, seq_len):
          j = (i + shift) % seq_len
          if seq[i] == seq[j]:
              match += 1
      return float(match) / float(seq_len)
  
  
new_contents: """Various utilities fot sequences manipulation"""
  from pysec.utils import xrange
  
  
  def ioc(seq, shift=1):
      """Return the index of coincidence"""
      match = 0
      seq_len = len(seq)
      for i in xrange(0, seq_len):
          j = (i + shift) % seq_len
          if seq[i] == seq[j]:
              match += 1
      return float(match) / float(seq_len)
  
  
  def contains_only(seq, *values):
      return all(el in values for el in seq)
  
  
subject: add contains_only()