class_docstr: This class is to calculate mean average precision.
    
code: def is_empty(self):
      return [
          calculator.heap_size for calculator in self._ap_calculators
      ] == [0 for _ in range(self._num_class)]
  
file_path: PaddleHub/modules/video/classification/videotag_tsn_lstm/resource/metrics/youtube8m/mean_average_precision_calculator.py
imports: import numpy
  from .None import average_precision_calculator
label_desc: Use image node_id 4 for calling the MeanAveragePrecisionCalculator obj's underlying member method code with example usage: obj.is_empty() and returns: unknown