Error regarding entity inheritance paradigm class

[easyang]

How do I fix this error?

Caused by: graphql.AssertException: Name must be non-null, non-empty and match [_A-Za-z][_0-9A-Za-z]* - was 'java.lang.Object'
at graphql.Assert.throwAssert(Assert.java:207)
at graphql.Assert.assertValidName(Assert.java:203)
at graphql.schema.GraphQLTypeReference.(GraphQLTypeReference.java:34)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getAttributeType(GraphQLJpaSchemaBuilder.java:1550)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getAttributeOutputType(GraphQLJpaSchemaBuilder.java:1524)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getObjectField(GraphQLJpaSchemaBuilder.java:1373)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.lambda$getEntityAttributesFields$23(GraphQLJpaSchemaBuilder.java:1338)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:212)
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:194)
at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1939)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:556)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:546)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:265)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:702)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getEntityAttributesFields(GraphQLJpaSchemaBuilder.java:1339)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.computeEntityObjectType(GraphQLJpaSchemaBuilder.java:1328)
at java.base/java.util.HashMap.computeIfAbsent(HashMap.java:1228)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getEntityObjectType(GraphQLJpaSchemaBuilder.java:1314)
at com.introproventures.graphql.jpa.query.schema.impl.GraphQLJpaSchemaBuilder.getQueryFieldByIdDefinition(GraphQLJpaSchemaBuilder.java:260)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:212)
at java.base/java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:194)
at java.base/java.util.HashMap$KeySpliterator.forEachRemaining(HashMap.java:1715)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:556)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:546)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:622)
at java.base/java.util.stream.AbstractPipeline.evaluateToArrayNode(AbstractPipeline.java:291)
at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:631)
at java.base/java.util.stream.ReferencePipeline.toArray(ReferencePipeline.java:637)
at java.base/java.util.stream.ReferencePipeline.toList(ReferencePipeline.java:642)