class_docstr: A model arch similar to FullyConnectedActor, except that the last layer
  is sampled from a Dirichlet distribution
code: def input_prototype(self):
      return rlt.FeatureData(torch.randn(1, self.state_dim))
  
imports: import math
  from typing import List, Optional
  import torch
  from reagent.core import types
  from reagent.core.parameters import CONTINUOUS_TRAINING_ACTION_RANGE
  from reagent.core.tensorboardX import SummaryWriterContext
  from reagent.models.base import ModelBase
  from reagent.models.fully_connected_network import FullyConnectedNetwork
  from torch.distributions import Dirichlet
  from torch.distributions.normal import Normal
label_desc: Use image node_id 2 for calling the DirichletFullyConnectedActor obj's underlying member method code with example usage: obj.input_prototype() and returns: rlt