Add Test Impact Analysis troubleshooting note for Python (#31978)

Author: vitor-de-araujo

content/en/tests/test_impact_analysis/troubleshooting/_index.md

@@ -48,6 +48,10 @@ Test Impact Analysis performs test impact analysis based on code coverage to det
 
 If you are authoring a commit that includes any of those cases, you can force-disable test skipping in Test Impact Analysis by adding `ITR:NoSkip` (case insensitive) anywhere in your Git commit message.
 
+### Packages incorrectly detected as third-party
+
+In Python, some packages, such as `sumy` and `sendgrid`, install modules under the `test.*` or `tests.*` package namespace. This can cause tests to be detected as third-party packages if they are located in a folder with the same name. If you use one of those packages, coverage data for tests may be incomplete, which may cause a test to be skipped when it should have been run. To avoid this issue, you can set the `DD_THIRD_PARTY_DETECTION_EXCLUDES` environment variable to a list of such third-party packages (for example, `DD_THIRD_PARTY_DETECTION_EXCLUDES=sumy,sendgrid`). This is a known issue that is scheduled to be resolved in a future version of `dd-trace-py`.
+
 ## Further reading
 
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