[MAINT] make proximal_operator a private module

doc/changes/latest.rst

@@ -29,8 +29,8 @@ Enhancements
 - :bdg-dark:`Code` :meth:`~maskers.NiftiLabelsMasker.generate_report` now uses appropriate cut coordinates when functional image is provided (:gh:`4099` by `Yasmin Mzayek`_ and `Nicolas Gensollen`_).
 - :bdg-info:`Plotting` When plotting thresholded statistical maps with a colorbar, the threshold value(s) will now be displayed as tick labels on the colorbar (:gh:`#2833` by `Nicolas Gensollen`_).
 - :bdg-success:`API` :class:`~maskers.NiftiSpheresMasker` now has ``generate_report`` method (:gh:`3102` by `Yasmin Mzayek`_ and `Nicolas Gensollen`_).
-- :bdg-primary:`Doc`  Mention the classification type (all-vs-one) in  :ref:`sphx_glr_auto_examples_02_decoding_plot_haxby_glm_decoding.py` (:gh:`4122` by `Tamer Gezici`_). 
-- :bdg-primary:`Doc`  Specify full form of LSS in  :ref:`sphx_glr_auto_examples_07_advanced_plot_beta_series.py` (:gh:`4141` by `Tamer Gezici`_). 
+- :bdg-primary:`Doc`  Mention the classification type (all-vs-one) in  :ref:`sphx_glr_auto_examples_02_decoding_plot_haxby_glm_decoding.py` (:gh:`4122` by `Tamer Gezici`_).
+- :bdg-primary:`Doc`  Specify full form of LSS in  :ref:`sphx_glr_auto_examples_07_advanced_plot_beta_series.py` (:gh:`4141` by `Tamer Gezici`_).
 - :bdg-primary:`Doc` Don't fetch tmaps in examples if tmaps aren't used in the example. (:gh:`4136` by `Christina Roßmanith`_).
 
 Changes
@@ -42,3 +42,4 @@ Changes
 - :bdg-dark:`Code` Private utility context manager ``write_tmp_imgs`` is refactored into function ``write_imgs_to_path`` (:gh:`4094` by `Yasmin Mzayek`_).
 - :bdg-danger:`Deprecation` :func:`~plotting.plot_surf_roi` will raise a warning if ``roi_map`` contains negative or non-integer values; in version 0.13 this will be a ``ValueError`` (:gh:`4131` by `Michelle Wang`_).
 - :bdg-dark:`Code` Remove leading underscore from non private functions to align with PEP8 (:gh:`4086` by `Rémi Gau`_).
+- :bdg-dark:`Code` Make ``decoding/proximal_operator`` explicitly private to align with PEP8 (:gh:`4153` by `Rémi Gau`_).

nilearn/_utils/tests/test_common.py

@@ -34,7 +34,7 @@ def test_number_public_functions():
     If this is intentional, then the number should be updated in the test.
     Otherwise it means that the public API of nilearn has changed by mistake.
     """
-    assert len({_[0] for _ in all_functions()}) == 215
+    assert len({_[0] for _ in all_functions()}) == 211
 
 
 def test_number_public_classes():

nilearn/decoding/space_net_solvers.py

@@ -24,13 +24,13 @@
     squared_loss,
     squared_loss_grad,
 )
-from .fista import mfista
-from .proximal_operators import (
+from ._proximal_operators import (
     prox_l1,
     prox_l1_with_intercept,
     prox_tvl1,
     prox_tvl1_with_intercept,
 )
+from .fista import mfista
 
 
 def _squared_loss_and_spatial_grad(X, y, w, mask, grad_weight):

nilearn/decoding/tests/test_fista.py

@@ -8,8 +8,8 @@
     squared_loss,
     squared_loss_grad,
 )
+from nilearn.decoding._proximal_operators import prox_l1
 from nilearn.decoding.fista import _check_lipschitz_continuous, mfista
-from nilearn.decoding.proximal_operators import prox_l1
 
 
 @pytest.mark.parametrize("scaling", list(np.logspace(-3, 3, num=7)))

nilearn/decoding/tests/test_operators.py

@@ -4,7 +4,7 @@
 import pytest
 from numpy.testing import assert_almost_equal
 
-from nilearn.decoding.proximal_operators import prox_l1, prox_tvl1
+from nilearn.decoding._proximal_operators import prox_l1, prox_tvl1
 
 
 def test_prox_l1_nonexpansiveness(rng, n_features=10):