fix: added if statement to filter out dir blob files (#63)

Fixes #62  🦕


Current version of sample doesnt check if blob is directory or .json file. Then, it  downloads as bytes and tries to parse json from the dir blob file which will cause error.

batch_process_documents_sample_v1beta3.py

@@ -78,9 +78,12 @@ def batch_process_documents(
 
     for i, blob in enumerate(blob_list):
         # Download the contents of this blob as a bytes object.
+        if ".json" not in blob.name:
+            return
+        # Only parses JSON files
         blob_as_bytes = blob.download_as_bytes()
-        document = documentai.types.Document.from_json(blob_as_bytes)
 
+        document = documentai.types.Document.from_json(blob_as_bytes)
         print(f"Fetched file {i + 1}")
 
         # For a full list of Document object attributes, please reference this page: https://googleapis.dev/python/documentai/latest/_modules/google/cloud/documentai_v1beta3/types/document.html#Document