code: def _generate_data(size):
      """For testing reasons only"""
      # return FeatureSpec('dummy', name=None, data='x' * size)
      return PlotSpec(
          data="x" * size, mapping=None, scales=[], layers=[]
      )
  
imports: import io
  import json
  import os
  from typing import Union
  from lets_plot._global_settings import get_global_bool, has_global_value, FRAGMENTS_ENABLED
label_desc: Use image node_id 5 for calling a global function with example usage: _generate_data(size) and returns: PlotSpec