code: def _opt_call_from_base_type(self, value):
      
      if isinstance(value, _BaseValue):
        value = self._call_from_base_type(value.b_val)
      return value
docs: Call _from_base_type() if necessary.
  
      If the value is a _BaseValue instance, unwrap it and call all
      _from_base_type() methods.  Otherwise, return the value
      unchanged.