def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def __init__(self, gan=None, config=None, trainer=None):
      super().__init__(config=config, gan=gan, trainer=trainer)
      self.d_grads = None
      self.g_grads = None