Create almost working proof of concept with new parsers

smnp/util/singleton.py

@@ -0,0 +1,14 @@
+from smnp.ast.parser import Parser
+
+
+def SingletonParser(function):
+    def wrapper(*args, **kwargs):
+        if not hasattr(function, 'instance'):
+            function.instance = function(*args, **kwargs)
+
+        if not isinstance(function.instance, Parser):
+            raise RuntimeError(f"Function {function.__name__} haven't returned Parser object")
+
+        return function.instance
+
+    return wrapper