fix: Import backports-datetime-fromisoformat only if needed, to fix PyPy 3.7 support

#415

Author: jpmckinney

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Fixed
+
+- Import backports-datetime-fromisoformat only if needed, to fix PyPy 3.7 support
+
 ## [0.20.0] - 2022-12-07
 
 ### Changed

flattentool/ODSReader.py

@@ -18,14 +18,15 @@
 from collections import OrderedDict
 from datetime import datetime
 
-import backports.datetime_fromisoformat
 import odf.opendocument
 from odf.table import Table, TableCell, TableRow
 
 # Backport for datetime.fromisoformat, which is new in Python 3.7
 try:
     _ = datetime.fromisoformat
 except AttributeError:
+    import backports.datetime_fromisoformat
+
     backports.datetime_fromisoformat.MonkeyPatch.patch_fromisoformat()