<!-- Please include a self-contained copy-pastable example that generates the issue if possible. Please be concise with code posted. See guidelines below on how to provide a good bug report: - Craft Minimal Bug Reports http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports - Minimal Complete Verifiable Examples https://stackoverflow.com/help/mcve Bug reports that follow these guidelines are easier to diagnose, and so are often handled much more quickly. --> **What happened**: The HighLevelGraphs example in docs/source/high-level-graphs.rst line 160 is missing a comma. **Environment**: - Dask version: latest master, 3a08bb32e736d51a758281a3abc0fc0dbec04efc - Python version: - Operating System: - Install method (conda, pip, source):