code: def _register_flows(self):
      vivado_ip = "vivado:ip"
      writer_passes = ["make_stamp", "vivadoaccelerator:write_hls"]
      self._writer_flow = register_flow(
          "write",
          writer_passes,
          requires=[vivado_ip],
          backend=self.name,
      )
      self._default_flow = vivado_ip
  
      fifo_depth_opt_passes = [
          "vivadoaccelerator:fifo_depth_optimization"
      ] + writer_passes
  
      register_flow(
          "fifo_depth_optimization",
          fifo_depth_opt_passes,
          requires=[vivado_ip],
          backend=self.name,
      )
  
file_path: hls4ml/hls4ml/backends/vivado_accelerator/vivado_accelerator_backend.py
imports: import os
  from hls4ml.backends import VivadoBackend
  from hls4ml.model.flow import register_flow
  from hls4ml.report import parse_vivado_report
label_desc: Use image node_id 7 for calling the VivadoAcceleratorBackend obj's underlying member method code with example usage: obj._register_flows() without return types