adding hashing and equality of AGraph objects

bingo/symbolic_regression/agraph/agraph.py

@@ -138,6 +138,7 @@ def __init__(self, use_simplification=False, equation=None):
         # self._needs_opt
         # self._modified
         self._init_command_array_and_const(equation)
+        self._hash = None
 
     # pylint: disable=attribute-defined-outside-init
     def _init_command_array_and_const(self, equation):
@@ -507,6 +508,15 @@ def save_onnx_model(self, file_name, model_name="bingo_equation"):
         with open(file_name, "wb") as onnx_file:
             onnx_file.write(model.SerializeToString())
 
+    def __hash__(self):
+        if self._modified or self._hash is None:
+            self._update()
+            self._hash = hash(tuple(map(tuple, self._simplified_command_array)))
+        return self._hash
+
+    def __eq__(self, other):
+        return hash(self) == hash(other)
+
     def __deepcopy__(self, memodict=None):
         duplicate = AGraph()
         self._copy_agraph_values_to_new_graph(duplicate)