code: def _write_validate(self):
          
          if self.colorspace is None:
              msg = ("Writing colr boxes without enumerated "
                     "colorspaces is not supported at this time.")
              self._dispatch_validation_error(msg, writing=True)
  
          if self.icc_profile is None:
              if self.colorspace not in [SRGB, GREYSCALE, YCC]:
                  msg = ("Colorspace should correspond to one of SRGB, "
                         "GREYSCALE, or YCC.")
                  self._dispatch_validation_error(msg, writing=True)
  
          self._validate(writing=True)
docs: In addition to constructor validation steps, run validation steps
          for writing.