fix: Add Python37DeprecationWarning (#241)

Author: holtskinner

README.rst

@@ -68,6 +68,16 @@ Python >= 3.7
 .. _active: https://devguide.python.org/devcycle/#in-development-main-branch
 .. _maintenance: https://devguide.python.org/devcycle/#maintenance-branches
 
+**NOTE**:
+Python 3.7 was marked as `unsupported`_ by the python community in June 2023.
+We recommend that all developers upgrade to Python 3.8 and newer as soon as
+they can. Support for Python 3.7 will be removed from all client libraries after
+January 1 2024. Client libraries that support Python 3.7 will continue to be available
+for download, but releases after January 1 2024 will only target Python 3.8 and
+newer.
+
+.. _unsupported: https://devguide.python.org/versions/#unsupported-versions
+
 Unsupported Python Versions
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Python <= 3.6

google/cloud/documentai_toolbox/__init__.py

@@ -14,6 +14,9 @@
 # limitations under the License.
 #
 
+import sys
+import warnings
+
 from google.cloud.documentai_toolbox import version as package_version
 
 __version__ = package_version.__version__
@@ -23,3 +26,19 @@
 from .wrappers import document, entity, page
 
 __all__ = (document, page, entity, converter, docai_utilities, gcs_utilities)
+
+
+class Python37DeprecationWarning(DeprecationWarning):  # pragma: NO COVER
+    """
+    Deprecation warning raised when Python 3.7 runtime is detected.
+    Python 3.7 support will be dropped after January 1, 2024.
+    """
+
+
+# Checks if the current runtime is Python 3.7.
+if sys.version_info.major == 3 and sys.version_info.minor == 7:  # pragma: NO COVER
+    message = (
+        "After January 1, 2024, new releases of this library will drop support "
+        "for Python 3.7."
+    )
+    warnings.warn(message, Python37DeprecationWarning)