fixes to notebook

lib/pt_trading/fit_method.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from abc import ABC, abstractmethod
 from enum import Enum
 from typing import Dict, Optional, cast
@@ -21,6 +23,15 @@ class PairsTradingFitMethod(ABC):
         "signed_scaled_disequilibrium",
         "pair",
     ]
+    @staticmethod
+    def create(config: Dict) -> PairsTradingFitMethod:
+        import importlib
+        fit_method_class_name = config.get("fit_method_class", None)
+        assert fit_method_class_name is not None
+        module_name, class_name = fit_method_class_name.rsplit(".", 1)
+        module = importlib.import_module(module_name)
+        fit_method = getattr(module, class_name)()
+        return cast(PairsTradingFitMethod, fit_method)
 
     @abstractmethod
     def run_pair(