code: def convert_to_strings(self, sequences, sizes=None):
          
          strings = []
          for x in xrange(len(sequences)):
              seq_len = sizes[x] if sizes is not None else len(sequences[x])
              string = self._convert_to_string(sequences[x], seq_len)
              strings.append(string)
          return strings
docs: Given a list of numeric sequences, returns the corresponding strings