diff --git a/README.md b/README.md
index ebcc010..1bfa537 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,10 @@
 A Python library for creating and consuming documents in
 [standard-bom format](https://sbom.siemens.io/latest/format.html).
 
-This library is mainly a wrapper for the official
-[cyclonedx-python-lib](https://github.com/CycloneDX/cyclonedx-python-lib/) library.
+"Standard BOM" is our Siemens-internal SBOM format based on the [Siemens CycloneDX Property Taxonomy](https://github.com/siemens/cyclonedx-property-taxonomy), which is 100% compatible with the CycloneDX.
+
+Every Standard BOM document is a 100% CycloneDX document, so both CycloneDX and Standard BOM formats are supported both
+for reading and writing SBOMs with this library.
 
 ## Installation
 
@@ -120,8 +122,8 @@ component.licenses = licenses
 
 In order to build this library on your local PC, and/or contribute to this library, mind the following prerequisites:
 
-- [Python](https://www.python.org/doc/versions/) > v3.10 - ideally > v3.12
-- [Poetry](https://python-poetry.org/) > v1.8.0
+- [Python](https://www.python.org/doc/versions/) >=3.10, <4.0
+- [Poetry](https://python-poetry.org/) >= v2.0
 
 ---
 Once you have those prerequisites you can perform following development tasks locally:
diff --git a/siemens_standard_bom/model.py b/siemens_standard_bom/model.py
index d7a5353..de3f894 100644
--- a/siemens_standard_bom/model.py
+++ b/siemens_standard_bom/model.py
@@ -596,7 +596,7 @@ def _set_supplier_if_missing(self) -> None:
         if not self.bom.metadata.supplier:
             self.bom.metadata.supplier = OrganizationalEntity(name='Siemens or its Affiliates')
 
-    def _set_metadata_property(self, property_name: str, value: str) -> None:
+    def _set_metadata_property(self, property_name: str, value: Optional[str | None]) -> None:
         existing = next(filter(lambda p: p.name == property_name,
                                self.bom.metadata.properties), None)
         if existing:
@@ -666,7 +666,7 @@ def profile(self) -> Optional[str]:
         return self._get_metadata_property(PROPERTY_PROFILE)
 
     @profile.setter
-    def profile(self, value: str) -> None:
+    def profile(self, value: Optional[str | None]) -> None:
         self._set_metadata_property(PROPERTY_PROFILE, value)
 
     @property
diff --git a/tests/test_model_sbom_component.py b/tests/test_model_sbom_component.py
index 4953b12..deee045 100644
--- a/tests/test_model_sbom_component.py
+++ b/tests/test_model_sbom_component.py
@@ -58,7 +58,10 @@ def test_property_setters(self) -> None:
         self.assertEqual("42.42", component.version)
 
         component.purl = PackageURL(type="generic", name="foo.zip")
-        self.assertEqual("foo.zip", component.purl.name)
+        if component.purl is not None:
+            self.assertEqual("foo.zip", component.purl.name)
+        else:
+            self.fail("component.purl should not be None")
 
         component.add_author(OrganizationalContact(name="Lex Luthor"))
         self.assertEqual("Lex Luthor", component.authors[0].name)
@@ -93,16 +96,16 @@ def test_direct_dependency(self) -> None:
         component = SbomComponent(Component(name="test"))
         self.assertFalse(component.direct_dependency)
 
-        component.direct_dependency = "true"  # type: ignore[assignment]
+        component.direct_dependency = "true"
         self.assertTrue(component.direct_dependency)
 
-        component.direct_dependency = "True"  # type: ignore[assignment]
+        component.direct_dependency = "True"
         self.assertTrue(component.direct_dependency)
 
-        component.direct_dependency = "False"  # type: ignore[assignment]
+        component.direct_dependency = "False"
         self.assertFalse(component.direct_dependency)
 
-        component.direct_dependency = "something"  # type: ignore[assignment]
+        component.direct_dependency = "something"
         self.assertFalse(component.direct_dependency)
 
     def test_internal(self) -> None:
diff --git a/tests/test_v3_parser_write.py b/tests/test_v3_parser_write.py
index 838bfe7..b305d09 100644
--- a/tests/test_v3_parser_write.py
+++ b/tests/test_v3_parser_write.py
@@ -152,7 +152,7 @@ def test_write_with_set_licenses(self) -> None:
         ))
 
         licenses = [LicenseExpression("MIT")]
-        comp.licenses = licenses   # type: ignore[assignment] # this is a mypy issue
+        comp.licenses = licenses
 
         sbom.add_component(comp)
         StandardBomParser.save(sbom, output_filename, with_dependencies=False)