class_docstr: Take mean of feature embeddings in time.
code: def compute_z(self, f0_scaled, ld_scaled):
      x = tf.concat([f0_scaled, ld_scaled], axis=-1)
      z = self.fc(x)
      return tf.reduce_mean(z, axis=1, keepdims=True)
  
imports: import ddsp
  from ddsp import spectral_ops
  from ddsp.training import nn
  import gin
  import tensorflow.compat.v2
label_desc: Use image node_id 2 for calling the AggregateFeaturesEncoder obj's underlying member method code with example usage: obj.compute_z(f0_scaled, ld_scaled) and returns: tf