docstr: The entropy of the policy distribution.
docstr_tok: ["The","entropy","of","the","policy","distribution","."]
code: def entropy(self):
      """The entropy of the policy distribution."""
      raise NotImplementedError
  
imports: from parl.core.fluid import layers
label_desc: Use image node_id 2 for calling the PolicyDistribution obj's underlying member method code with example usage: obj.entropy() without return types