docs(samples): Added Human Review Request Sample (#357)

- Illustrates how to call `review_document()` to send a processed document to Human in the Loop (HITL)

Co-authored-by: Anthonios Partheniou <partheniou@google.com>

packages/google-cloud-documentai/samples/snippets/review_document_sample.py

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+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# [START documentai_review_document]
+
+from google.api_core.client_options import ClientOptions
+from google.cloud import documentai_v1 as documentai
+
+# TODO(developer): Uncomment these variables before running the sample.
+# project_id = 'YOUR_PROJECT_ID'
+# location = 'YOUR_PROCESSOR_LOCATION' # Format is 'us' or 'eu'
+# processor_id = 'YOUR_PROCESSOR_ID' # Create processor in Cloud Console
+# file_path = '/path/to/local/pdf'
+# mime_type = 'application/pdf'  # https://cloud.google.com/document-ai/docs/file-types
+
+
+def review_document_sample(
+    project_id: str, location: str, processor_id: str, file_path: str, mime_type: str
+):
+    # You must set the api_endpoint if you use a location other than 'us', e.g.:
+    opts = ClientOptions(api_endpoint=f"{location}-documentai.googleapis.com")
+
+    # Create a client
+    client = documentai.DocumentProcessorServiceClient(client_options=opts)
+
+    # Make Processing Request
+    inline_document = process_document(
+        project_id, location, processor_id, file_path, mime_type
+    )
+
+    # Get the full resource name of the human review config, e.g.:
+    # projects/project_id/locations/location/processor/processor_id/humanReviewConfig
+    human_review_config = client.human_review_config_path(
+        project_id, location, processor_id
+    )
+
+    # Options are DEFAULT, URGENT
+    priority = documentai.ReviewDocumentRequest.Priority.DEFAULT
+
+    # Configure the human review request
+    request = documentai.ReviewDocumentRequest(
+        inline_document=inline_document,
+        human_review_config=human_review_config,
+        enable_schema_validation=False,
+        priority=priority,
+    )
+
+    # Make a request for human review of the processed document
+    operation = client.review_document(request=request)
+
+    # Print operation name, can be used to check status of the request
+    print(operation.operation.name)
+
+
+def process_document(
+    project_id: str, location: str, processor_id: str, file_path: str, mime_type: str
+) -> documentai.Document:
+    # You must set the api_endpoint if you use a location other than 'us', e.g.:
+    opts = ClientOptions(api_endpoint=f"{location}-documentai.googleapis.com")
+
+    client = documentai.DocumentProcessorServiceClient(client_options=opts)
+
+    # The full resource name of the processor, e.g.:
+    # projects/project_id/locations/location/processor/processor_id
+    # You must create new processors in the Cloud Console first
+    name = client.processor_path(project_id, location, processor_id)
+
+    # Read the file into memory
+    with open(file_path, "rb") as image:
+        image_content = image.read()
+
+    # Load Binary Data into Document AI RawDocument Object
+    raw_document = documentai.RawDocument(content=image_content, mime_type=mime_type)
+
+    # Configure the process request
+    request = documentai.ProcessRequest(name=name, raw_document=raw_document)
+
+    result = client.process_document(request=request)
+
+    return result.document
+
+
+# [END documentai_review_document]

packages/google-cloud-documentai/samples/snippets/review_document_sample_test.py

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+# Copyright 2022 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+
+from samples.snippets import review_document_sample
+
+location = "us"
+project_id = os.environ["GOOGLE_CLOUD_PROJECT"]
+processor_id = "b7054d67d76c39f1"
+file_path = "resources/invoice.pdf"
+mime_type = "application/pdf"
+
+
+def test_process_documents(capsys):
+    review_document_sample.review_document_sample(
+        project_id=project_id,
+        location=location,
+        processor_id=processor_id,
+        file_path=file_path,
+        mime_type=mime_type,
+    )
+    out, _ = capsys.readouterr()
+
+    assert "projects/" in out
+    assert "locations/" in out
+    assert "operations/" in out