made access to error codes and niter of estimator nicer

Author: davidsebfischer

batchglm/models/base/estimator.py

@@ -41,6 +41,14 @@ def __init__(
         self._error_codes = None
         self._niter = None
 
+    @property
+    def error_codes(self):
+        return self._error_codes
+
+    @property
+    def niter(self):
+        return self._niter
+
     @property
     def loss(self):
         return self._loss