move crossover_gene from ga.crossover to gene.basegene.

tensorneat/algorithm/neat/gene/node/base.py

@@ -1,3 +1,4 @@
+import jax, jax.numpy as jnp
 from .. import BaseGene
 
 
@@ -8,5 +9,12 @@ class BaseNodeGene(BaseGene):
     def __init__(self):
         super().__init__()
 
+    def crossover(self, state, randkey, gene1, gene2):
+        return jnp.where(
+            jax.random.normal(randkey, gene1.shape) > 0,
+            gene1,
+            gene2,
+        )
+
     def forward(self, state, attrs, inputs, is_output_node=False):
         raise NotImplementedError