code: def get_seq(seq_record, codon_positions, aminoacids=False, degenerate=None):
      
      Sequence = namedtuple('Sequence', ['seq', 'warning'])
  
      if codon_positions not in [None, '1st', '2nd', '3rd', '1st-2nd', 'ALL']:
          raise WrongParameterFormat("`codon_positions` argument should be any of the following"
                                     ": 1st, 2nd, 3rd, 1st-2nd or ALL")
      if aminoacids:
          aa = seq_record.translate()
          if '*' in aa:
              warning = "Gene {0}, sequence {1} contains stop codons '*'".format(seq_record.gene_code,
                                                                                 seq_record.voucher_code)
          else:
              warning = None
          return Sequence(seq=aa, warning=warning)
  
      if degenerate:
          return Sequence(seq=seq_record.degenerate(degenerate), warning=None)
  
      if codon_positions == '1st':
          return Sequence(seq=seq_record.first_codon_position(), warning=None)
      elif codon_positions == '2nd':
          return Sequence(seq=seq_record.second_codon_position(), warning=None)
      elif codon_positions == '3rd':
          return Sequence(seq=seq_record.third_codon_position(), warning=None)
      elif codon_positions == '1st-2nd':
          return Sequence(seq=seq_record.first_and_second_codon_positions(), warning=None)
      else:  # None and ALL
          return Sequence(seq=str(seq_record.seq), warning=None)
docs: Checks parameters such as codon_positions, aminoacids... to return the
      required sequence as string.
  
      Parameters:
          seq_record (SeqRecordExpanded object):
          codon_positions (str):
          aminoacids (boolean):
  
      Returns:
          Namedtuple containing ``seq (str)`` and ``warning (str)``.