Add docstring to perf_builder()

Bug: b/244275800
Change-Id: Ic305dafe57d63f3ca0cabe6841732773cbc21c37
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/274721
Commit-Queue: Junji Watanabe <jwata@google.com>
Auto-Submit: Junji Watanabe <jwata@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38042}
diff --git a/infra/config/config.star b/infra/config/config.star
index 9b84939..7b27bd6 100755
--- a/infra/config/config.star
+++ b/infra/config/config.star
@@ -619,6 +619,17 @@
     )
 
 def perf_builder(name, perf_cat, **kwargs):
+    """Add a perf builder.
+
+    Args:
+      name: builder name (str).
+      perf_cat: the category + name for the /perf/ console, or None to omit from the console.
+      **kwargs: Pass on to webrtc_builder / luci.builder.
+    Returns:
+      A luci.builder.
+
+    Notifications are also disabled.
+    """
     add_milo(name, {"perf": perf_cat})
     properties = make_goma_properties()
     properties["builder_group"] = "client.webrtc.perf"