Correct way to pass extra args

docs/notebooks/customize.ipynb

@@ -163,7 +163,7 @@
     "\n",
     "The `is_missing` method should return a boolean mask, resampled at the `freq` frequency, the same as the indicator output (same as `count`), where True values are for elements that are considered missing and masked on the output.\n",
     "\n",
-    "To add additional arguments, one should override the `__init__` (receiving those arguments) and the `validate` static method, which validates them. See example below and the docstrings in the module.\n",
+    "To add additional arguments, one should override the `__init__` (receiving those arguments) and the `validate` static method, which validates them. The options are then stored in the `options` property of the instance. See example below and the docstrings in the module.\n",
     "\n",
     "When registering the class with the `xclim.core.checks.register_missing_method` decorator, the keyword arguments will be registered as options for the missing method. "
    ]
@@ -185,9 +185,9 @@
     "    def __init__(self, max_n: int = 5):\n",
     "        super().__init__(max_n=max_n)\n",
     "\n",
-    "    def is_missing(self, null, count, freq, max_n=5):\n",
+    "    def is_missing(self, null, count, freq):\n",
     "        \"\"\"Return a boolean mask where True values are for elements that are considered missing and masked on the output.\"\"\"\n",
-    "        return null.resample(time=freq).map(longest_run, dim=\"time\") >= max_n\n",
+    "        return null.resample(time=freq).map(longest_run, dim=\"time\") >= self.options['max_n']\n",
     "\n",
     "    @staticmethod\n",
     "    def validate(max_n):\n",