DONOTUSE -> None

      If you choose to pass in a tuple, the tuple will be directly used as the

      charset during featurization.

      If you pass in None, the charset passed to the featurizer will be None.

      This is not recommended.

      Pass "DONOTUSE" to charset not pass a charset to the featurizer.

      Pass None to charset not pass a charset to the featurizer.

    max_length: Optional[int] (default: None)

      max_length should be equal to or larger than the length of the longest

        "nucleic": ('A', 'C', 'G', 'T', 'U', '(i)', 'R', 'Y', 'K', 'M', 'S',

                    'W', 'B', 'D', 'H', 'V', 'N', '-'),

        "ATCGN": ('A', 'T', 'C', 'G'),

        "DONOTUSE": "DONOTUSE"

    }

    # Initialize instance variables

      try:

        self.charset = charsets[charset]

      except KeyError:

        logger.warning("Charset is invalid string. Treating as DONOTUSE...")

        self.charset = "DONOTUSE"

        logger.warning("Charset is invalid string. Treating as None...")

        self.charset = None

    elif isinstance(charset, tuple):

      self.charset = charset

    else:

    # Initialize featurizer

    try:

      if self.charset != "DONOTUSE" and self.max_length != -1:

      if self.charset is not None and self.max_length != -1:

        featurizer = featurizer(charset=self.charset,

                                max_length=self.max_length)

      elif self.charset != "DONOTUSE" and self.max_length == -1:

      elif self.charset is not None and self.max_length == -1:

        featurizer = featurizer(charset=self.charset)

      elif self.charset == "DONOTUSE" and self.max_length != -1:

      elif self.charset is None and self.max_length != -1:

        featurizer = featurizer(max_length=self.max_length)

      elif self.charset == "DONOTUSE" and self.max_length == -1:

      elif self.charset is None and self.max_length == -1:

        featurizer = featurizer()

    except:

      logger.exception("Sorry! Your featurizer may not be supported yet.")