class_docstr: Create plots for `PredictPlot`
  
  Methods
  -------
  plot_matplotlib : plot using matplotlib
  plot_plotly : plot using plotly
class_docstr_tok: ["Create","plots","for","`","PredictPlot","`","Methods","--","--","--","-","plot_matplotlib",":","plot","using","matplotlib","plot_plotly",":","plot","using","plotly"]
code: def prepare_data(self, class_idx):
      target = self.plot_obj.target[class_idx]
      box_color = next(self.box_colors)
      box_df = self.plot_obj.df[["x", target]].rename(
          columns={target: "y"}
      )
      line_df = self.plot_obj.target_lines[class_idx].rename(
          columns={target + "_q2": "y"}
      )
      return target, box_df, line_df, box_color
  
imports: from .styles import _prepare_plot_style, _axes_modify, _display_percentile, _modify_legend_axes, _get_axes_label
  import numpy
  from itertools import cycle
  import plotly.express
  import matplotlib
  import matplotlib.pyplot
  from matplotlib.gridspec import GridSpecFromSubplotSpec
  from mpl_toolkits.axes_grid1.inset_locator import inset_axes
  import matplotlib.patheffects
  import plotly.graph_objects
label_desc: Use image node_id 2 for calling the PredictPlotEngine obj's underlying member method code with example usage: obj.prepare_data(class_idx) and returns: target,  box_df,  line_df,  box_color