code: def get_input_dict_placeholders(self):
      shape = (None, self.params["n_channels"])
      features = {
          "waveform": placeholder(
              tf.float32, shape=shape, name="waveform"
          ),
          "audio_id": placeholder(tf.string, name="audio_id"),
      }
      return features
  
imports: import importlib
  from typing import Any, Dict, Optional, Tuple
  import tensorflow
  from tensorflow.signal import hann_window, inverse_stft, stft
  from ..utils.tensor import pad_and_partition, pad_and_reshape
label_desc: Use image node_id 2 for calling the WaveformInputProvider obj's underlying member method code with example usage: obj.get_input_dict_placeholders() and returns: features