Use calcfunction for getitem in For loop workgraph

aiida_workgraph/engine/workgraph.py

@@ -30,7 +30,7 @@
     construct_awaitable,
 )
 from aiida.engine.processes.workchains.workchain import Protect, WorkChainSpec
-from aiida.engine import run_get_node
+from aiida.engine import calcfunction, run_get_node
 from aiida_workgraph.utils import create_and_pause_process
 from aiida_workgraph.task import Task
 from aiida_workgraph.utils import get_nested_dict, update_nested_dict
@@ -920,7 +920,19 @@ def check_for_conditions(self) -> bool:
         if should_run:
             self.reset()
             self.set_tasks_state(condition_tasks, "SKIPPED")
-            self.ctx["i"] = self.ctx._sequence[self.ctx._count]
+
+            @calcfunction
+            def __getitem__(sequence, count):
+                value = sequence[count.value]
+                # only convert value f not already orm type because sequence
+                # might be builtin collection with orm types so a conversion is
+                # not needed and would raise an error
+                if isinstance(value, orm.Data):
+                    return value
+                else:
+                    return orm.to_aiida_type(value)
+
+            self.ctx["i"] = __getitem__(self.ctx._sequence, self.ctx._count)
         self.ctx._count += 1
         return should_run