docs: def get_datetime(formatted_str, user_fmt=None):
          # type: (AnyStr, Optional[AnyStr]) -> datetime
          """get datetime() object from string formatted %Y-%m-%d %H:%M:%S
  
          Examples:
              >>> StringClass.get_datetime('2008-11-9')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('2008/11/9')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('20081109')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('11/9/2008')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('11-9-2008')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('11/09/08')
              datetime.datetime(2008, 11, 9, 0, 0)
              >>> StringClass.get_datetime('2008-11-9 11:09')
              datetime.datetime(2008, 11, 9, 11, 9)
              >>> StringClass.get_datetime('2008-11-9 11:09:52')
              datetime.datetime(2008, 11, 9, 11, 9, 52)
          """
          date_fmts = ['%m-%d-%Y', '%Y-%m-%d', '%m-%d-%y', '%y-%m-%d']
          date_fmts += [d.replace('-', '/') for d in date_fmts]
          date_fmts += [d.replace('-', '') for d in date_fmts]
          time_fmts = ['%H:%M', '%H:%M:%S']
          fmts = date_fmts + ['%s %s' % (d, t) for d in date_fmts for t in time_fmts]
          if user_fmt is not None:
              if is_string(user_fmt):
                  fmts.insert(0, str(user_fmt))
              elif isinstance(user_fmt, list):
                  fmts = user_fmt + fmts
              elif isinstance(user_fmt, tuple):
                  for fff in user_fmt:
                      fmts.insert(0, fff)
          flag = False
          for fmt in fmts:
              try:
                  org_time = time.strptime(formatted_str, fmt)
                  flag = True
                  break
              except ValueError:
                  pass
          if not flag:
              raise ValueError('The DATETIME must be one of the formats: %s' % ','.join(fmts))
          else:
              return datetime(org_time.tm_year, org_time.tm_mon, org_time.tm_mday,
                              org_time.tm_hour, org_time.tm_min, org_time.tm_sec)