How to get literal label value in OWL?

Question

I created ontology in desctop Protege. It consists of two classes - test1 and test2. Then I declared labels for them. First label with no datatype, second - literal. The OWL-file content is below. The dif is presense of string 'rdf:datatype="&rdfs;Literal"' While trying to get labels via owlready2, got an error 'ValueError: Cannot read literal of datatype 305!' for literal-type label.

Here is OWL-file content:

<?xml version="1.0"?>


<!DOCTYPE rdf:RDF [
    <!ENTITY owl "http://www.w3.org/2002/07/owl#" >
    <!ENTITY xsd "http://www.w3.org/2001/XMLSchema#" >
    <!ENTITY rdfs "http://www.w3.org/2000/01/rdf-schema#" >
    <!ENTITY rdf "http://www.w3.org/1999/02/22-rdf-syntax-ns#" >
]>


<rdf:RDF xmlns="http://www.semanticweb.org/jdrey/ontologies/2020/11/test#"
     xml:base="http://www.semanticweb.org/jdrey/ontologies/2020/11/test"
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns:owl="http://www.w3.org/2002/07/owl#"
     xmlns:xsd="http://www.w3.org/2001/XMLSchema#"
     xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
    <owl:Ontology rdf:about="http://www.semanticweb.org/jdrey/ontologies/2020/11/test"/>
    


    <!-- 
    ///////////////////////////////////////////////////////////////////////////////////////
    //
    // Classes
    //
    ///////////////////////////////////////////////////////////////////////////////////////
     -->

    


    <!-- http://www.semanticweb.org/jdrey/ontologies/2020/11/test:test1 -->

    <owl:Class rdf:about="http://www.semanticweb.org/jdrey/ontologies/2020/11/test:test1">
        <rdfs:label>label_test1</rdfs:label>
    </owl:Class>
    


    <!-- http://www.semanticweb.org/jdrey/ontologies/2020/11/test:test2 -->

    <owl:Class rdf:about="http://www.semanticweb.org/jdrey/ontologies/2020/11/test:test2">
        <rdfs:label rdf:datatype="&rdfs;Literal">label_test2</rdfs:label>
    </owl:Class>
</rdf:RDF>

This is code for printing labels for subclasses:

from owlready2 import *
owlready2.JAVA_EXE = r'c:\Users\JDrey\AppData\Local\JetBrains\PyCharm Community Edition with Anaconda plugin 2020.1.2\jbr\bin\java.exe'
my_world = World()
onto = my_world.get_ontology(r'd:\temp\OWL\test_owl.owl').load()
for elem in list(Thing.subclasses(world = my_world)):
    print(elem.label)

Here is output with error message:

['label_test1']
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-6-5e6c14d62ea5> in <module>
      5 onto = my_world.get_ontology(r'd:\temp\OWL\test_owl.owl').load()
      6 for elem in list(Thing.subclasses(world = my_world)):
----> 7     print(elem.label)

D:\anaconda\envs\new_env\lib\site-packages\owlready2\entity.py in __getattr__(Class, attr)
    561         values = Class.__dict__.get(attr)
    562         if values is None:
--> 563           values = Prop._get_values_for_class(Class)
    564           type.__setattr__(Class, attr, values)
    565         return values

D:\anaconda\envs\new_env\lib\site-packages\owlready2\prop.py in _get_values_for_individual(Prop, entity)
    309   def _get_values_for_individual(Prop, entity):
    310     return IndividualValueList((entity.namespace.ontology._to_python(o, d) for o, d in entity.namespace.world._get_triples_sp_od(entity.storid, Prop.storid)),
--> 311                                entity, Prop)
    312 
    313   _get_value_for_class  = _get_value_for_individual

D:\anaconda\envs\new_env\lib\site-packages\owlready2\prop.py in __init__(self, l, obj, Prop)
   1045   __slots__ = ["_Prop"]
   1046   def __init__(self, l, obj, Prop):
-> 1047     list.__init__(self, l)
   1048     self._obj  = obj
   1049     self._Prop = Prop

D:\anaconda\envs\new_env\lib\site-packages\owlready2\prop.py in <genexpr>(.0)
    308 
    309   def _get_values_for_individual(Prop, entity):
--> 310     return IndividualValueList((entity.namespace.ontology._to_python(o, d) for o, d in entity.namespace.world._get_triples_sp_od(entity.storid, Prop.storid)),
    311                                entity, Prop)
    312 

D:\anaconda\envs\new_env\lib\site-packages\owlready2\namespace.py in _to_python(self, o, d, main_type, main_onto, default_to_none)
    260       if   o in _universal_abbrev_2_datatype: return _universal_abbrev_2_datatype[o]
    261       else: return self.world._get_by_storid(o, None, main_type, main_onto, None, default_to_none)
--> 262     else: return from_literal(o, d)
    263     raise ValueError
    264 

D:\anaconda\envs\new_env\lib\site-packages\owlready2\base.py in from_literal(o, d)
     56   if d == 0: return o
     57   datatype, parser = _universal_abbrev_2_datatype_parser.get(d) or (None, None)
---> 58   if parser is None: raise ValueError("Cannot read literal of datatype %s!" % repr(d))
     59   return parser(o)
     60 

ValueError: Cannot read literal of datatype 305!

How can I get the label value for test2?