Update python.mdx

adding parent inheritance info

Author: sfanahata

platform-includes/performance/traces-sampler-as-sampler/python.mdx

@@ -4,6 +4,13 @@ def traces_sampler(sampling_context):
     # along with anything in the global namespace to compute the sample rate
     # or sampling decision for this transaction
 
+    # Use the parent sampling decision if we have an incoming trace.
+    # Note: we strongly recommend respecting the parent sampling decision,
+    # as this ensures your traces will be complete!
+    parent_sampling_decision = sampling_context.get("parent_sampled")
+    if parent_sampling_decision is not None:
+        return float(parent_sampling_decision)
+
     if "...":
         # These are important - take a big sample
         return 0.5