**Apache Airflow version**:
2.0 / master

**Environment**:

breeze

**What happened**:

Using this DAG:

```py
from airflow.operators.bash import BashOperator
from airflow.operators.python import task
from airflow.models import DAG
from airflow.utils.task_group import TaskGroup

@task
def show():
    print("Cats are awesome!")

with DAG(
    "using_task_group",
    default_args={'owner': 'airflow'},
    start_date=days_ago(2),
    schedule_interval=None,
) as dag3:
    start_task = BashOperator(
        task_id="start_task",
        bash_command="echo start",
    )

    end_task = BashOperator(
        task_id="end_task",
        bash_command="echo end",
    )

    with TaskGroup(group_id="show_tasks") as tg1:
        previous_show = show()
        for _ in range(100):
            next_show = show()
            previous_show >> next_show
            previous_show = next_show
```
I get:
```
Broken DAG: [/files/dags/test.py] Traceback (most recent call last):
  File "/opt/airflow/airflow/models/baseoperator.py", line 410, in __init__
    task_group.add(self)
  File "/opt/airflow/airflow/utils/task_group.py", line 140, in add
    raise DuplicateTaskIdFound(f"Task id '{key}' has already been added to the DAG")
airflow.exceptions.DuplicateTaskIdFound: Task id 'show_tasks.show' has already been added to the DAG
```

If I remove the task group the task are generated as expected.

**What you expected to happen**:

I expect to be able to generate tasks dynamically using TaskGroup and task decoratos.

**How to reproduce it**:

Use the DAG from above.

**Anything else we need to know**:

N/A

tests/operators/test_python.py
example_context = {"Hello": "World"}
        with set_current_context(example_context):
            pass
        with pytest.raises(
            AirflowException,
        ):
            get_current_context()
    def test_nested_context(self):
        """
        Nested execution context should be supported in case the user uses multiple context managers.
        Each time the execute method of an operator is called, we set a new 'current' context.
        This test verifies that no matter how many contexts are entered - order is preserved
        """
        max_stack_depth = 15
        ctx_list = []
        for i in range(max_stack_depth):
            
            new_context = {"ContextId": i}
            
            ctx_obj = set_current_context(new_context)
            ctx_obj.__enter__()  
            ctx_list.append(ctx_obj)
        for i in reversed(range(max_stack_depth)):
            
            ctx = get_current_context()
            assert ctx["ContextId"] == i
            
            ctx_list[i].__exit__(None, None, None)
class MyContextAssertOperator(BaseOperator):