CLN: Drop lags parameter from Panel.shift (#14041)

Author: gfyoung

doc/source/whatsnew/v0.19.0.txt

@@ -891,6 +891,7 @@ Removal of prior version deprecations/changes
 - ``pd.Categorical`` has dropped setting of the ``ordered`` attribute directly in favor of the ``set_ordered`` method (:issue:`13671`)
 - ``pd.Categorical`` has dropped the ``levels`` attribute in favour of ``categories`` (:issue:`8376`)
 - ``DataFrame.to_sql()`` has dropped the ``mysql`` option for the ``flavor`` parameter (:issue:`13611`)
+- ``Panel.shift()`` has dropped the ``lags`` parameter in favour of ``periods`` (:issue:`14041`)
 - ``pd.Index`` has dropped the ``diff`` method in favour of ``difference`` (:issue:`13669`)
 
 - ``Series.to_csv`` has dropped the ``nanRep`` parameter in favor of ``na_rep`` (:issue:`13804`)

pandas/core/panel.py

@@ -35,7 +35,7 @@
 from pandas.core.ops import _op_descriptions
 from pandas.core.series import Series
 from pandas.tools.util import cartesian_product
-from pandas.util.decorators import (deprecate, Appender, deprecate_kwarg)
+from pandas.util.decorators import (deprecate, Appender)
 
 _shared_doc_kwargs = dict(
     axes='items, major_axis, minor_axis',
@@ -1234,7 +1234,6 @@ def count(self, axis='major'):
 
         return self._wrap_result(result, axis)
 
-    @deprecate_kwarg(old_arg_name='lags', new_arg_name='periods')
     def shift(self, periods=1, freq=None, axis='major'):
         """
         Shift index by desired number of periods with an optional time freq.

pandas/tests/test_panel.py

@@ -881,20 +881,6 @@ def setUp(self):
         self.panel.minor_axis.name = None
         self.panel.items.name = None
 
-    def test_panel_warnings(self):
-        with tm.assert_produces_warning(FutureWarning):
-            shifted1 = self.panel.shift(lags=1)
-
-        with tm.assert_produces_warning(False):
-            shifted2 = self.panel.shift(periods=1)
-
-        tm.assert_panel_equal(shifted1, shifted2)
-
-        with tm.assert_produces_warning(False):
-            shifted3 = self.panel.shift()
-
-        tm.assert_panel_equal(shifted1, shifted3)
-
     def test_constructor(self):
         # with BlockManager
         wp = Panel(self.panel._data)