class_docstr: bar shifter is just a wrapper for matplotlib bar chart
  which automatically computes the position of the bars
  you need to specify how many groups of bars are gonna be
  and the size of such groups. The frst time you call it,
  will plot the first element for every group, then the second one
  and so on
class_docstr_tok: ["bar","shifter","is","just","a","wrapper","for","matplotlib","bar","chart","which","automatically","computes","the","position","of","the","bars","you","need","to","specify","how","many","groups","of","bars","are","gon","na","be","and","the","size","of","such","groups",".","The","frst","time","you","call","it",",","will","plot","the","first","element","for","every","group",",","then","the","second","one","and","so","on"]
code: def __init__(self, g_number, g_size, ax, scale=0.8):
      self.g_number = g_number
      self.g_size = g_size
      self.ax = ax
      self.i = 0
      self.width = (1.0 / g_size) * scale
      self.colors = plt.get_cmap()(np.linspace(0, 1, self.g_size))
  
file_path: sklearn-evaluation/src/sklearn_evaluation/plot/matplotlib/bar.py
imports: import numpy
  import matplotlib.pyplot
  from sklearn_evaluation.plot.matplotlib.data_grid import DataGrid
  from sklearn_evaluation.plot.util import set_default_ax
label_desc: Use image node_id 1 to create a new BarShifter object  with example: obj = BarShifter(g_number, g_size, ax, scale)