code: def eval(self) -> datetime:
      dttm_expression, delta, unit = self.value
      dttm = dttm_expression.eval()
      if unit.lower() == "quarter":
          delta = delta * 3
          unit = "month"
      return dttm + parse_human_timedelta(f"{delta} {unit}s", dttm)
  
imports: import calendar
  import logging
  import re
  from datetime import datetime, timedelta
  from functools import lru_cache
  from time import struct_time
  from typing import Optional
  import pandas
  import parsedatetime
  from dateutil.parser import parse
  from dateutil.relativedelta import relativedelta
  from flask_babel import lazy_gettext
  from holidays import country_holidays
  from pyparsing import CaselessKeyword, Forward, Group, Optional, ParseException, ParserElement, ParseResults, pyparsing_common, quotedString, Suppress
  from superset.commands.chart.exceptions import TimeDeltaAmbiguousError, TimeRangeAmbiguousError, TimeRangeParseFailError
  from superset.constants import LRU_CACHE_MAX_SIZE, NO_TIME_RANGE
label_desc: Use image node_id 2 for calling the EvalDateAddFunc obj's underlying member method code with example usage: obj.eval() and returns: unknown