class_docstr: Configure annotations (for pie and bar charts).
  
  Examples
  --------
  .. jupyter-execute::
      :linenos:
      :emphasize-lines: 6
  
      from lets_plot import *
      LetsPlot.setup_html()
      data = {'name': ['a', 'b', 'c', 'd', 'b'], 'value': [40, 90, 10, 50, 20 ] }
      ggplot(data) + geom_pie(aes(slice='value', fill='name'), size=15, hole=0.4, \
                              stat='identity', tooltips = 'none', \
                              labels=layer_labels().line('@value'))
docstr: Initialize self.
  
  Parameters
  ----------
  variables : list of str
      Variable names to place in the annotation with default formatting.
code: def __init__(self, variables: List[str] = None):
      """
      Initialize self.
  
      Parameters
      ----------
      variables : list of str
          Variable names to place in the annotation with default formatting.
  
      """
  
      self._formats: List = []
      self._lines: List = None
      self._variables = variables
      self._size = None
      super().__init__("labels", name=None)
  
file_path: lets-plot/python-package/lets_plot/plot/annotation.py
imports: from typing import List
  from lets_plot.plot.core import FeatureSpec, _filter_none
label_desc: Use image node_id 1 to create a new layer_labels object from inherited base classes: FeatureSpec with example: obj = layer_labels(variables)