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"""
Important classes of Spark SQL and DataFrames:

    - :class:`pyspark.sql.SparkSession`
      Main entry point for :class:`DataFrame` and SQL functionality.
    - :class:`pyspark.sql.DataFrame`
      A distributed collection of data grouped into named columns.
    - :class:`pyspark.sql.Column`
      A column expression in a :class:`DataFrame`.
    - :class:`pyspark.sql.Row`
      A row of data in a :class:`DataFrame`.
    - :class:`pyspark.sql.GroupedData`
      Aggregation methods, returned by :func:`DataFrame.groupBy`.
    - :class:`pyspark.sql.DataFrameNaFunctions`
      Methods for handling missing data (null values).
    - :class:`pyspark.sql.DataFrameStatFunctions`
      Methods for statistics functionality.
    - :class:`pyspark.sql.functions`
      List of built-in functions available for :class:`DataFrame`.
    - :class:`pyspark.sql.types`
      List of data types available.
    - :class:`pyspark.sql.Window`
      For working with window functions.
"""
from pyspark.sql.types import Row
from pyspark.sql.context import SQLContext, HiveContext, UDFRegistration
from pyspark.sql.session import SparkSession
from pyspark.sql.column import Column
from pyspark.sql.catalog import Catalog
from pyspark.sql.dataframe import DataFrame, DataFrameNaFunctions, DataFrameStatFunctions
from pyspark.sql.group import GroupedData
from pyspark.sql.observation import Observation
from pyspark.sql.readwriter import DataFrameReader, DataFrameWriter
from pyspark.sql.window import Window, WindowSpec
from pyspark.sql.pandas.group_ops import PandasCogroupedOps


__all__ = [
    "SparkSession",
    "SQLContext",
    "HiveContext",
    "UDFRegistration",
    "DataFrame",
    "GroupedData",
    "Column",
    "Catalog",
    "Observation",
    "Row",
    "DataFrameNaFunctions",
    "DataFrameStatFunctions",
    "Window",
    "WindowSpec",
    "DataFrameReader",
    "DataFrameWriter",
    "PandasCogroupedOps",
]
