## Combine - BinaryCombineFn Lambda

BinaryCombineFn is used for implementing combiners that are more easily expressed as binary operations.

Since Beam v2.13.0, you can also use lambda or method reference in order to create the BinaryCombineFn.

Kata: Implement the summation of BigInteger using lambda or method reference.

Refer to SerializableBiFunction.
Refer to the Beam Programming Guide "Combine" section for more information.