docs: def from_optional_dict(cls, d: Optional[dict],
                             force_snake_case: bool=True,force_cast: bool=False, restrict: bool=True) -> TOption[T]:
          """From dict to optional instance.
  
          :param d: Dict
          :param force_snake_case: Keys are transformed to snake case in order to compliant PEP8 if True
          :param force_cast: Cast forcibly if True
          :param restrict: Prohibit extra parameters if True
          :return: Instance
  
          Usage:
  
              >>> from owlmixin.samples import Human
              >>> Human.from_optional_dict(None).is_none()
              True
              >>> Human.from_optional_dict({}).get()  # doctest: +NORMALIZE_WHITESPACE
              Traceback (most recent call last):
                  ...
              owlmixin.errors.RequiredError:
              .        ∧,,_∧      ,___________________
                   ⊂ ( ･ω･ )つ-  <  Required error
                 ／／/     /::/     `-------------------
                 |::|/⊂ヽノ|::|」
              ／￣￣旦￣￣￣／|
              ＿＿＿＿＿＿／  | |
              |------ー----ー|／
              <BLANKLINE>
              `owlmixin.samples.Human#id: int` is empty!!
              <BLANKLINE>
                  * If `id` is certainly required, specify anything.
                  * If `id` is optional, change type from `int` to `TOption[int]`
              <BLANKLINE>
          """
          return TOption(cls.from_dict(d,
                                       force_snake_case=force_snake_case,
                                       force_cast=force_cast,
                                       restrict=restrict) if d is not None else None)