code: def format(self, node):
      params = self._default_function_params(node)
  
      types = ["i", "f", "c", "o"]
      params["weights"] = ""
      for t in types:
          params["weights"] += f"kernel_{t}_{str(node.index)},"
      for t in types:
          params[
              "weights"
          ] += f"recurrent_kernel_{t}_{str(node.index)},"
      for t in types:
          params["weights"] += "bias_{}_{}{}".format(
              t, str(node.index), "," if t != "o" else ""
          )
  
      return self.template.format(**params)
  
imports: from hls4ml.backends.backend import get_backend
  from hls4ml.backends.template import FunctionCallTemplate, LayerConfigTemplate
  from hls4ml.model.layers import GRU, LSTM, SimpleRNN
label_desc: Use image node_id 2 for calling the LSTMFunctionTemplate obj's underlying member method code with example usage: obj.format(node) and returns: self