org.apache.flink.api.common.functions.InvalidTypesException: The return type of function 'retrieve(ReplyGraph.java:33)' could not be determined automatically, due to type erasure. You can give type information hints by using the returns(...) method on the result of the transformation call, or by letting your function implement the 'ResultTypeQueryable' interface.

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The return type of function 'retrieve(ReplyGraph.java:33)' could not be determined automatically, due to type erasure. You can give type information hints by using the returns(...) method on the result of the transformation call, or by letting your function implement the 'ResultTypeQueryable' interface.
org.apache.flink.api.common.functions.InvalidTypesException: The generic type parameters of 'Tuple3' are missing. It seems that your compiler has not stored them into the .class file. Currently, only the Eclipse JDT compiler preserves the type information necessary to use the lambdas feature type-safely. See the documentation for more information about how to compile jobs containing lambda expressions.
at org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameter(TypeExtractor.java:1316)
at org.apache.flink.api.java.typeutils.TypeExtractor.validateLambdaGenericParameters(TypeExtractor.java:1302)
at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:346)
at org.apache.flink.api.java.typeutils.TypeExtractor.getUnaryOperatorReturnType(TypeExtractor.java:304)
at org.apache.flink.api.java.typeutils.TypeExtractor.getMapReturnTypes(TypeExtractor.java:119)
at org.apache.flink.quickstart.exercise2.ReplyGraph.retrieve(ReplyGraph.java:33)
at org.apache.flink.quickstart.exercise2.ReplyGraph.main(ReplyGraph.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)

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