Using `result_value` in method tasks

According to https://gitlab.esrf.fr/workflow/ewoks/ewokscore/-/blob/main/ewokscore/methodtask.py#L14, the output of a method task is stored in the outputs under the key result_value.

However, I can't seem to make this work with a simple graph:

from ewokscore import execute_graph
from ewokscore.utils import qualname


def add(a, b):
    return a + b


def divide(a, b):
    return a / b


nodes = [
    {
        "id": "add",
        "task_type": "method",
        "task_identifier": qualname(add),
        "default_inputs": [{"name": "a", "value": 6}, {"name": "b", "value": 4}],
    },
    {
        "id": "divide",
        "task_type": "method",
        "task_identifier": qualname(divide),
        "default_inputs": [{"name": "a", "value": 6}],
    },
]
links = [
    {
        "source": "add",
        "target": "divide",
        "data_mapping": [{"source_output": "result_value", "target_input": "b"}],
    }
]
graph = {"nodes": nodes, "links": links}

execute_graph(graph)

I am trying to reuse the result of add as a arg of divide but this code raises KeyError: 'result_value'. Am I doing something wrong ?

Full Traceback

Traceback (most recent call last):
  File ".../ewokscore/graph.py", line 25, in execute_graph
    return graph.execute(varinfo=varinfo)
  File ".../ewokscore/graph.py", line 641, in execute
    task = self.instantiate_task_static(node, tasks=tasks, varinfo=varinfo)
  File ".../ewokscore/graph.py", line 302, in instantiate_task_static
    inittask.add_dynamic_inputs(
  File ".../ewokscore/inittask.py", line 185, in add_dynamic_inputs
    dynamic_inputs[input_arg] = source_results[output_arg]
  File ".../ewokscore/variable.py", line 174, in __getitem__
    return self.value[key]
KeyError: 'result_value'

ewokscore version: 0.0.3a0