fix(src): Refactor valid_part_conforms for PDF/A compliance levels

src/ocrmypdf/pdfa.py

@@ -120,7 +120,7 @@ def file_claims_pdfa(filename: Path):
                 'output': 'pdf',
                 'conformance': 'No PDF/A metadata in XMP',
             }
-        valid_part_conforms = {'1A', '1B', '2A', '2B', '2U', '3A', '3B', '3U'}
+        valid_part_conforms = {'1a', '1b', '2a', '2b', '2u', '3a', '3b', '3u'}
         conformance = f'PDF/A-{pdfmeta.pdfa_status}'
         pdfa_dict: dict[str, str | bool] = {}
         if pdfmeta.pdfa_status in valid_part_conforms:

src/ocrmypdf/pluginspec.py

@@ -492,7 +492,7 @@ def generate_pdfa(
         pdf_version: The minimum PDF version that the output file should be.
             At its own discretion, the PDF/A generator may raise the version,
             but should not lower it.
-        pdfa_part: The desired PDF/A compliance level, such as ``'2B'``.
+        pdfa_part: The desired PDF/A compliance level, such as ``'2b'``.
         progressbar_class: The class of a progress bar, which must implement
             the ProgressBar protocol. If None, no progress is reported.
         stop_on_soft_error: If there is an "soft error" such that PDF/A generation