public ObjectNode getDefinition(DefinitionKey key) {
        return this.definitions.get(key);
    }
Retrieve the previously added definition for the specified type.

@param key definition key to look-up associated definition for
@return JSON schema definition (or null if none is present)
@see #putDefinition(ResolvedType, ObjectNode, CustomDefinitionProviderV2)
jsonschema-generator/src/main/java/com/github/victools/jsonschema/generator/impl/SchemaGenerationContextImpl.java