add note about vertical lines

Author: afeld

assignments.md

@@ -120,7 +120,7 @@ Note [the Final Project submission](final_project.md#submission) is slightly dif
    - The column and the GeoJSON properties have values that match
 - **`SettingWithCopyWarning`:** [How to fix](https://www.dataquest.io/blog/settingwithcopywarning/)
 - **`input()` stuck:** Jupyter can be a bit buggy when dealing with interactive input. If it seems to get stuck or you aren't seeing a prompt when you'd expect one, try clicking the `{{coding_env_kernel_name.title()}}` menu then `Restart Kernel`.
-- **The values are out of order along the axis of a Plotly chart:** Make sure that:
+- **In a visualization, the values are out of order along the axis, or you're seeing vertical/zig-zag-y lines:** Make sure that:
    - The values are integers/floats/[timestamps](https://plotly.com/python/line-charts/#line-plots-on-date-axes), not strings, where applicable.
    - [Line charts: The column used for the X axis is sorted.](https://plotly.com/python/line-charts/#data-order-in-line-charts)
 - **`AttributeError: partially initialized module 'orjson' has no attribute 'OPT_NON_STR_KEYS'`:** Add the following cell before your other Plotly code, then `Restart and run all`{% if id == "nyu" %} (⏩){% endif %}.