## Copyright (c) 2021, NVIDIA CORPORATION.## Licensed under the Apache License, Version 2.0 (the "License");# you may not use this file except in compliance with the License.# You may obtain a copy of the License at## http://www.apache.org/licenses/LICENSE-2.0## Unless required by applicable law or agreed to in writing, software# distributed under the License is distributed on an "AS IS" BASIS,# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.# See the License for the specific language governing permissions and# limitations under the License.#fromtypingimportAnyimportdask.dataframeasddfrom.operatorimportColumnSelector,Operator

[docs]classStatOperator(Operator):""" Base class for statistical operator classes. This adds a 'fit' and 'finalize' method on top of the Operator class. """

[docs]deffit(self,col_selector:ColumnSelector,ddf:dd.DataFrame)->Any:"""Calculate statistics for this operator, and return a dask future to these statistics, which will be computed by the workflow."""raiseNotImplementedError("""The dask operations needed to return a dictionary of uncomputed statistics.""")

[docs]deffit_finalize(self,dask_stats):"""Finalize statistics calculation - the workflow calls this function with the computed statistics from the 'fit' object'"""raiseNotImplementedError("""Follow-up operations to convert dask statistics in to member variables""")

[docs]defclear(self):"""zero and reinitialize all relevant statistical properties"""raiseNotImplementedError("clear isn't implemented for this op!")

[docs]defset_storage_path(self,new_path,copy=False):"""Certain stat operators need external storage - for instance Categorify writes out parquet files containing the categorical mapping. When we save the operator, we also want to save these files as part of the bundle. Implementing this method lets statoperators bundle their dependent files into the new path that we're writing out (note that this could happen after the operator is created) """