code: def seq_sha1(seq, normalize=True):
      
  
      seq = normalize_sequence(seq) if normalize else seq
      bseq = seq.encode("ascii")
      return hashlib.sha1(bseq).hexdigest()
docs: returns unicode sha1 hexdigest for sequence `seq`.
  
      >>> seq_sha1('')
      'da39a3ee5e6b4b0d3255bfef95601890afd80709'
  
      >>> seq_sha1('ACGT')
      '2108994e17f6cca9ff2352ada92b6511db076034'
  
      >>> seq_sha1('acgt')
      '2108994e17f6cca9ff2352ada92b6511db076034'
  
      >>> seq_sha1('acgt', normalize=False)
      '9482340281b5fc8f2a298dbbd6b82fe42159b6c5'