How to solve "Step definition is not found" error: StepDefinitionNotFoundError - pytest

Question

Here is my feature file - a.feature:
Scenario Outline: Some outline
Given something
When <thing> is moved to <position>
Then something else
Examples:
| thing | position |
| 1 | 1 |
and save it in /tmp/a.feature
Here is my pytest step file (/tmp/a.py):
from pytest_bdd import (
given,
scenario,
then,
when,
)
#scenario('./x.feature', 'Some outline')
def test_some_outline():
"""Some outline."""
#given('something')
def something():
"""something."""
pass
#when('<thing> is moved to <position>')
def thing_is_moved_to_position(thing, position):
assert isinstance(thing, int)
assert isinstance(position, int)
#then('something else')
def something_else():
"""something else."""
pass
When I run it:
$ pwd
/tmp
$ pytest ./a.py
............
............
E pytest_bdd.exceptions.StepDefinitionNotFoundError: Step definition is not found: When "1 is moved to 1". Line 3 in scenario "Some outline" in the feature "/tmp/x.feature"
/home/cyan/.local/lib/python3.10/site-packages/pytest_bdd/scenario.py:192: StepDefinitionNotFoundError
============= short test summary info =============
FAILED x.py::test_some_outline[1-1] - pytest_bdd.exceptions.StepDefinitionNotFoundError: Step definition is not found: When "1 is moved to 1". Line 3 in scenario "Some outli...
============ 1 failed in 0.09s ============