How to use the ipyparallel.controller.dependency.Dependency function in ipyparallel

def _validate_dependency(self, dep):
        """validate a dependency.

        For use in `set_flags`.
        """
        if dep is None or isinstance(dep, string_types + (AsyncResult, Dependency)):
            return True
        elif isinstance(dep, (list,set, tuple)):
            for d in dep:
                if not isinstance(d, string_types + (AsyncResult,)):
                    return False
        elif isinstance(dep, dict):
            if set(dep.keys()) != set(Dependency().as_dict().keys()):
                return False
            if not isinstance(dep['msg_ids'], list):
                return False
            for d in dep['msg_ids']:
                if not isinstance(d, string_types):
                    return False
        else:
            return False

def _validate_dependency(self, dep):
        """validate a dependency.

        For use in `set_flags`.
        """
        if dep is None or isinstance(dep, string_types + (AsyncResult, Dependency)):
            return True
        elif isinstance(dep, (list,set, tuple)):
            for d in dep:
                if not isinstance(d, string_types + (AsyncResult,)):
                    return False
        elif isinstance(dep, dict):
            if set(dep.keys()) != set(Dependency().as_dict().keys()):
                return False
            if not isinstance(dep['msg_ids'], list):
                return False
            for d in dep['msg_ids']:
                if not isinstance(d, string_types):
                    return False
        else:
            return False

        return True

# get targets as a set of bytes objects
        # from a list of unicode objects
        targets = md.get('targets', [])
        targets = set(map(cast_bytes, targets))

        retries = md.get('retries', 0)
        self.retries[msg_id] = retries

        # time dependencies
        after = md.get('after', None)
        if after:
            after = Dependency(after)
            if after.all:
                if after.success:
                    after = Dependency(after.difference(self.all_completed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
                if after.failure:
                    after = Dependency(after.difference(self.all_failed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
            if after.check(self.all_completed, self.all_failed):
                # recast as empty set, if `after` already met,
                # to prevent unnecessary set comparisons
                after = MET
        else:
            after = MET

def _render_dependency(self, dep):
        """helper for building jsonable dependencies from various input forms."""
        if isinstance(dep, Dependency):
            return dep.as_dict()
        elif isinstance(dep, AsyncResult):
            return dep.msg_ids
        elif dep is None:
            return []
        else:
            # pass to Dependency constructor
            return list(Dependency(dep))

retries = md.get('retries', 0)
        self.retries[msg_id] = retries

        # time dependencies
        after = md.get('after', None)
        if after:
            after = Dependency(after)
            if after.all:
                if after.success:
                    after = Dependency(after.difference(self.all_completed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
                if after.failure:
                    after = Dependency(after.difference(self.all_failed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
            if after.check(self.all_completed, self.all_failed):
                # recast as empty set, if `after` already met,
                # to prevent unnecessary set comparisons
                after = MET
        else:
            after = MET

        # location dependencies
        follow = Dependency(md.get('follow', []))

        timeout = md.get('timeout', None)
        if timeout:

md = msg['metadata']
        msg_id = header['msg_id']
        self.all_ids.add(msg_id)

        # get targets as a set of bytes objects
        # from a list of unicode objects
        targets = md.get('targets', [])
        targets = set(map(cast_bytes, targets))

        retries = md.get('retries', 0)
        self.retries[msg_id] = retries

        # time dependencies
        after = md.get('after', None)
        if after:
            after = Dependency(after)
            if after.all:
                if after.success:
                    after = Dependency(after.difference(self.all_completed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
                if after.failure:
                    after = Dependency(after.difference(self.all_failed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
            if after.check(self.all_completed, self.all_failed):
                # recast as empty set, if `after` already met,
                # to prevent unnecessary set comparisons

)
                if after.failure:
                    after = Dependency(after.difference(self.all_failed),
                                success=after.success,
                                failure=after.failure,
                                all=after.all,
                    )
            if after.check(self.all_completed, self.all_failed):
                # recast as empty set, if `after` already met,
                # to prevent unnecessary set comparisons
                after = MET
        else:
            after = MET

        # location dependencies
        follow = Dependency(md.get('follow', []))

        timeout = md.get('timeout', None)
        if timeout:
            timeout = float(timeout)

        job = Job(msg_id=msg_id, raw_msg=raw_msg, idents=idents, msg=msg,
                 header=header, targets=targets, after=after, follow=follow,
                 timeout=timeout, metadata=md,
        )
        # validate and reduce dependencies:
        for dep in after,follow:
            if not dep: # empty dependency
                continue
            # check valid:
            if msg_id in dep or dep.difference(self.all_ids):
                self.queue_map[msg_id] = job