Error in parsing dweet.io swagger description

[izzyblues]

Hi,
I tried to parse the following Swagger description: https://dweet.io/play/definition/

Unfortunately, Swagger4J returns this exception:
java.lang.AssertionError: Can not add API to Resource Listing; path already exists at com.smartbear.swagger4j.impl.ResourceListingImpl.addApi(ResourceListingImpl.java:85) at com.smartbear.swagger4j.impl.SwaggerReaderImpl.readResourceListing(SwaggerReaderImpl.java:68) at com.smartbear.swagger4j.impl.SwaggerReaderImpl.readResourceListing(SwaggerReaderImpl.java:43) at com.smartbear.swagger4j.Swagger.readSwagger(Swagger.java:81)

This is the source code:
ResourceListing resourceListing = Swagger.readSwagger("https://dweet.io/play/definition/");

Am I doing something wrong?

Thank you.