text: # Copyright (c) 2009-2015, Florian Finkernagel. All rights reserved.
  
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  """A wrapper around ggplot2 ( http://had.co.nz/ggplot2/ ) and 
  plotnine (https://plotnine.readthedocs.io/en/stable/index.html )
  
  Takes a pandas.DataFrame object, then add layers with the various add_xyz
  functions (e.g. add_scatter).
  
  Referr to the ggplot/plotnine documentation about the layers (geoms), and simply
  replace geom_* with add_*.
  See http://docs.ggplot2.org/0.9.3.1/index.html or 
  https://plotnine.readthedocs.io/en/stable/index.html<Paste>
  
  You do not need to seperate aesthetics from values - the wrapper
  will treat a parameter as value if and only if it is not a column name.
  (so y = 0 is a value, color = 'blue 'is a value - except if you have a column
  'blue', then it's a column!. And y = 'value' doesn't work, but that seems to be a ggplot issue).
  
  When the DataFrame is passed to the plotting library:
      - row indices are truned into columns with 'reset_index'
      - multi level column indices are flattend by concatenating them with ' '
          -> (X, 'mean) becomes 'x mean'
  
  R Error messages are not great - most of them translate to 'one or more columns were not found',
  but they can appear as a lot of different actual messages such as
      - argument "env" is missing, with no defalut
      - object 'y' not found
      - object 'dat_0' not found
      - requires the follewing missing aesthetics: x
      - non numeric argument to binary operator
  without actually quite pointing at what is strictly the offending value.
  Also, the error appears when rendering (or printing in ipython notebook),
  not when adding the layer.
  """
  #from .plot_r import Plot, plot_heatmap, multiplot, MultiPagePlot, convert_dataframe_to_r
  from .base import _PlotBase
  #from . import plot_nine
  from .plot_nine import Plot, Expression, Scalar
  
  all = [Plot, Expression, Scalar]
  