class_docstr: Detect outliers using the standard deviation within a rolling window.
  
  Outliers are the array elements outside `sigma` standard deviations from
  the smoothed trend line, as calculated from the trend line residuals.
  
  The rolling window is controlled by parameters shared with the
  `rolling` operation via the base class RollingBase, to make it
  simpler to use the same settings for both.
code: def _process(self, element, key=None):
      return element.map(self._process_layer, Element)
  
imports: import numpy
  import pandas
  import param
  from packaging.version import Version
  from ..core import Element, Operation
  from ..core.data import PandasInterface
  from ..core.util import _PANDAS_FUNC_LOOKUP, pandas_version
  from ..element import Scatter
label_desc: Use image node_id 2 for calling the rolling_outlier_std obj's underlying member method code with example usage: obj._process(element, key) and returns: element