# Dense Subgraphs

**URL:** <https://discuss.pennylane.ai/t/dense-subgraphs/1181>\
**Category:** Strawberry Fields\
**Created:** [July 6, 2021, 4:20pm UTC](https://discuss.pennylane.ai/t/dense-subgraphs/1181 "2021-07-06T16:20:52Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![\_risto](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/_risto/32/237_2.png) [@\_risto](https://discuss.pennylane.ai/u/_risto)\
**Post date:** [July 6, 2021, 4:20pm UTC](https://discuss.pennylane.ai/t/dense-subgraphs/1181/1 "2021-07-06T16:20:52Z")

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Hi.

While running:

sub = list(range(20, 30)) [plot.graph](https://strawberryfields.readthedocs.io/en/stable/code/api/strawberryfields.apps.plot.graph.html#strawberryfields.apps.plot.graph)(pl\_graph, sub) in [Dense Subgraphs — Strawberry Fields](https://strawberryfields.ai/photonics/apps/run_tutorial_dense.html) , I get: ValueError: source code string cannot contain null bytes

 ![image](https://canada1.discourse-cdn.com/flex012/uploads/pennylane/original/1X/94a82a4bf2d7679d1b5ac913fb10f869f28faf3d.png)

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**Author:** ![josh](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/josh/32/100_2.png) [@josh](https://discuss.pennylane.ai/u/josh)\
**Post date:** [July 6, 2021, 5:17pm UTC](https://discuss.pennylane.ai/t/dense-subgraphs/1181/2 "2021-07-06T17:17:55Z")

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Hi @_risto! It looks like the bottom of the error message has been cutoff, would you be able to post the full traceback 🙂