fix type annotation for protobuf serialized data (open-telemetry#3699)

exporter/opentelemetry-exporter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/_log_exporter/__init__.py

@@ -103,15 +103,15 @@ def __init__(
             )
         self._shutdown = False
 
-    def _export(self, serialized_data: str):
+    def _export(self, serialized_data: bytes):
         data = serialized_data
         if self._compression == Compression.Gzip:
             gzip_data = BytesIO()
             with gzip.GzipFile(fileobj=gzip_data, mode="w") as gzip_stream:
                 gzip_stream.write(serialized_data)
             data = gzip_data.getvalue()
         elif self._compression == Compression.Deflate:
-            data = zlib.compress(bytes(serialized_data))
+            data = zlib.compress(serialized_data)
 
         return self._session.post(
             url=self._endpoint,

exporter/opentelemetry-exporter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/metric_exporter/__init__.py

@@ -139,15 +139,15 @@ def __init__(
             preferred_temporality, preferred_aggregation
         )
 
-    def _export(self, serialized_data: str):
+    def _export(self, serialized_data: bytes):
         data = serialized_data
         if self._compression == Compression.Gzip:
             gzip_data = BytesIO()
             with gzip.GzipFile(fileobj=gzip_data, mode="w") as gzip_stream:
                 gzip_stream.write(serialized_data)
             data = gzip_data.getvalue()
         elif self._compression == Compression.Deflate:
-            data = zlib.compress(bytes(serialized_data))
+            data = zlib.compress(serialized_data)
 
         return self._session.post(
             url=self._endpoint,

exporter/opentelemetry-exporter-otlp-proto-http/src/opentelemetry/exporter/otlp/proto/http/trace_exporter/__init__.py

@@ -101,15 +101,15 @@ def __init__(
             )
         self._shutdown = False
 
-    def _export(self, serialized_data: str):
+    def _export(self, serialized_data: bytes):
         data = serialized_data
         if self._compression == Compression.Gzip:
             gzip_data = BytesIO()
             with gzip.GzipFile(fileobj=gzip_data, mode="w") as gzip_stream:
                 gzip_stream.write(serialized_data)
             data = gzip_data.getvalue()
         elif self._compression == Compression.Deflate:
-            data = zlib.compress(bytes(serialized_data))
+            data = zlib.compress(serialized_data)
 
         return self._session.post(
             url=self._endpoint,

exporter/opentelemetry-exporter-zipkin-proto-http/src/opentelemetry/exporter/zipkin/proto/http/v2/__init__.py

@@ -45,7 +45,7 @@ def content_type():
 
     def serialize(
         self, spans: Sequence[Span], local_endpoint: NodeEndpoint
-    ) -> str:
+    ) -> bytes:
         encoded_local_endpoint = self._encode_local_endpoint(local_endpoint)
         # pylint: disable=no-member
         encoded_spans = zipkin_pb2.ListOfSpans()