code: def fulfill(self, value):
          
  
          assert self._state==self.PENDING
  
          self._state=self.FULFILLED;
          self.value = value
          for callback in self._callbacks:
              try:
                  callback(value)
              except Exception:
                  # Ignore errors in callbacks
                  pass
          # We will never call these callbacks again, so allow
          # them to be garbage collected.  This is important since
          # they probably include closures which are binding variables
          # that might otherwise be garbage collected.
          self._callbacks = []
docs: Fulfill the promise with a given value.