### Apache Airflow version

Other Airflow 2 version (please specify below)

### What happened

Airflow 2.3.4 (but actual code seems to have same behaviour).

I have mapped task with xcom value.

I want to get xcom value of particular instance or xcom values of all task instances.

I am using standard REST API method /dags/{dag_id}/dagRuns/{dag_run_id}/taskInstances/{task_id}/xcomEntries/{xcom_key}

And it throws an error
`
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/orm/query.py&#34;, line 2850, in one_or_none
    return self._iter().one_or_none()
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 1510, in one_or_none
    return self._only_one_row(
  File &#34;/home/airflow/.local/lib/python3.9/site-packages/sqlalchemy/engine/result.py&#34;, line 614, in _only_one_row
    raise exc.MultipleResultsFound(
sqlalchemy.exc.MultipleResultsFound: Multiple rows were found when one or none was required
`

Is it any way of getting xcom of mapped tasks via API?

### What you think should happen instead

_No response_

### How to reproduce

Make dag with mapped task. Return xcom value in every task. Try to get xcom value via API.

### Operating System

ubuntu 20.04

### Versions of Apache Airflow Providers

_No response_

### Deployment

Other

### Deployment details

Standard

### Anything else

_No response_

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)

def _create_task_instance(
        operator_class,
        *,
        dag_id,
        execution_date=None,
        session=None,
        **operator_kwargs,
    ) -> TaskInstance:
        with dag_maker(dag_id=dag_id, session=session):
            operator_class(**operator_kwargs)
        if execution_date is None:
            dagrun_kwargs = {}
        else:
            dagrun_kwargs = {"execution_date": execution_date}
        (ti,) = dag_maker.create_dagrun(**dagrun_kwargs).task_instances
        return ti
    return _create_task_instance
@pytest.fixture()
def create_task_of_operator(dag_maker):
    def _create_task_of_operator(operator_class, *, dag_id, session=None, **operator_kwargs):
        with dag_maker(dag_id=dag_id, session=session):
            task = operator_class(**operator_kwargs)
        return task
    return _create_task_of_operator
@pytest.fixture
def session():