common: reverse for operations

circle/common/operations.py

 from inspect import getargspec
 from logging import getLogger
 
-from .models import activity_context
+from .models import activity_context, activity_code_separator
 
 from django.core.exceptions import PermissionDenied
 
@@ -170,6 +170,15 @@ class OperatedMixin(object):
             else:
                 yield op
 
+    def get_operation_from_activity_code(self, activity_code):
+        sep = activity_code_separator
+        ops = getattr(self, operation_registry_name, {}).values()
+        for op in ops:
+            if activity_code.endswith(sep + op.activity_code_suffix):
+                return op
+        else:
+            return None
+
 
 def register_operation(op_cls, op_id=None, target_cls=None):
     """Register the specified operation with the target class.