class_docstr: List of scales
  
  This class has methods the simplify the handling of
  the ggplot object scales
class_docstr_tok: ["List","of","scales","This","class","has","methods","the","simplify","the","handling","of","the","ggplot","object","scales"]
docstr: Transform values in a dataframe.
  
  Returns dataframe
docstr_tok: ["Transform","values","in","a","dataframe",".","Returns","dataframe"]
code: def transform_df(self, data: pd.DataFrame) -> pd.DataFrame:
      """
      Transform values in a dataframe.
  
      Returns dataframe
      """
      if (len(data) == 0) or (len(self) == 0):
          return data
  
      # Each scale transforms the columns it understands
      for sc in self:
          data = sc.transform_df(data)
      return data
  
imports: from __future__ import annotations
  import itertools
  import typing
  from contextlib import suppress
  from typing import List
  from warnings import warn
  import numpy
  import pandas.api.types
  from .._utils import array_kind
  from .._utils.registry import Registry
  from ..exceptions import PlotnineError, PlotnineWarning
  from ..mapping.aes import aes_to_scale
  from .scale import scale
label_desc: Use image node_id 14 for calling the Scales obj's underlying member method code with example usage: obj.transform_df(data) and returns: data, data