Implemented a first and basic version of a Rete rule engine

src/core/sheerka/services/sheerka_service.py

@@ -1,6 +1,6 @@
 from dataclasses import dataclass
 
-from core.global_symbols import NotFound
+from core.global_symbols import NotFound, ErrorObj
 from core.utils import sheerka_deepcopy
 
 
@@ -14,8 +14,9 @@ class BaseService:
     Base class for services
     """
 
-    def __init__(self, sheerka):
+    def __init__(self, sheerka, order=999):
         self.sheerka = sheerka
+        self.order = order  # initialisation order. The lowest is initialized first
 
     def initialize(self):
         """
@@ -46,3 +47,8 @@ class BaseService:
         Store/record the value of an attribute
         """
         self.sheerka.record_var(context, self.NAME, var_name, getattr(self, var_name))
+
+
+@dataclass()
+class FailedToCompileError(Exception, ErrorObj):
+    cause: list