Don't prematurely handle event streams

This removes event streams from the generated deser methods, as they
aren't handled there. They will eventually be handled by the protocol
python implementation on a higher level. This also removes the
attempt at handling them as if they were a blob stream, as they are
currently handled elsewhere.

Author: JordonPhillips

codegen/smithy-python-codegen/src/main/java/software/amazon/smithy/python/codegen/StructureGenerator.java

@@ -41,6 +41,7 @@
 import software.amazon.smithy.model.traits.InputTrait;
 import software.amazon.smithy.model.traits.OutputTrait;
 import software.amazon.smithy.model.traits.SensitiveTrait;
+import software.amazon.smithy.model.traits.StreamingTrait;
 import software.amazon.smithy.python.codegen.generators.MemberDeserializerGenerator;
 import software.amazon.smithy.python.codegen.generators.MemberSerializerGenerator;
 
@@ -417,6 +418,9 @@ private void deserializeMembers(Collection<MemberShape> members) {
         int index = 0;
         for (MemberShape member : members) {
             var target = model.expectShape(member.getTarget());
+            if (target.hasTrait(StreamingTrait.class) && target.isUnionShape()) {
+                continue;
+            }
             writer.write("""
                     case $L:
                         kwargs[$S] = ${C|}

codegen/smithy-python-codegen/src/main/java/software/amazon/smithy/python/codegen/integration/RestJsonProtocolGenerator.java

@@ -314,10 +314,15 @@ protected void deserializePayloadBody(
 
         var symbolProvider = context.symbolProvider();
         var memberName = symbolProvider.toMemberName(payloadBinding.getMember());
+        var target = context.model().expectShape(payloadBinding.getMember().getTarget());
 
-        if (payloadBinding.getMember().getMemberTrait(context.model(), StreamingTrait.class).isPresent()) {
-            writer.addImport("smithy_core.aio.types", "AsyncBytesReader");
-            writer.write("kwargs[$S] = AsyncBytesReader(http_response.body)", memberName);
+        if (target.hasTrait(StreamingTrait.class)) {
+            // If the target is a union, nothing needs to be done here. The stream deserializer will
+            // take the response body directly and handle it.
+            if (target.isBlobShape()) {
+                writer.addImport("smithy_core.aio.types", "AsyncBytesReader");
+                writer.write("kwargs[$S] = AsyncBytesReader(http_response.body)", memberName);
+            }
             return;
         }
 
@@ -334,7 +339,6 @@ protected void deserializePayloadBody(
                     """);
         }
 
-        var target = context.model().expectShape(payloadBinding.getMember().getTarget());
         var deserializerSymbol = symbolProvider.toSymbol(target);
 
         writer.write("if body:").indent();