Backport #10041, #10065 (#10068)

* decim is actually used for epochs (#10041)

* Don't warn when using decim with ICA.fit() on epochs (#10065)

* Don't warn when using decim with ICA.fit() on epochs

Follow-up to #10041

* Fix tests

Co-authored-by: Alexandre Gramfort <alexandre.gramfort@m4x.org>

mne/preprocessing/ica.py

@@ -565,9 +565,6 @@ def fit(self, inst, picks=None, start=None, stop=None, decim=None,
         decim : int | None
             Increment for selecting only each n-th sampling point. If ``None``,
             all samples  between ``start`` and ``stop`` (inclusive) are used.
-
-            .. note:: This parameter only has an effect if ``inst`` is
-                      `~mne.io.Raw` data.
         reject, flat : dict | None
             Rejection parameters based on peak-to-peak amplitude (PTP)
             in the continuous data. Signal periods exceeding the thresholds
@@ -620,8 +617,8 @@ def fit(self, inst, picks=None, start=None, stop=None, decim=None,
         if not isinstance(inst, BaseRaw):
             ignored_params = [
                 param_name for param_name, param_val in zip(
-                    ('start', 'stop', 'decim', 'reject', 'flat'),
-                    (start, stop, decim, reject, flat)
+                    ('start', 'stop', 'reject', 'flat'),
+                    (start, stop, reject, flat)
                 )
                 if param_val is not None
             ]

mne/preprocessing/tests/test_ica.py

@@ -1120,7 +1120,6 @@ def test_fit_methods(method, tmp_path):
     (
         ('start', 0),
         ('stop', 500),
-        ('decim', 2),
         ('reject', dict(eeg=500e-6)),
         ('flat', dict(eeg=1e-6))
     )