docs: def str_to_dt(val):
      """ Return a datetime object if the string value represents one
  
      Epoch integer or an ISO 8601 compatible string is
      supported.
  
      :param val: str
      :return: datetime
      :raise: ValueError
      """
  
      if isinstance(val, dt):
          return val
  
      try:
          if val.isdigit():
              return dt.utcfromtimestamp(float(val))
          else:
              return dt.strptime(val, '%Y-%m-%dT%H:%M:%S.%f')
      except (AttributeError, TypeError):
          raise ValueError