code: def test_firfilter_zi(dtype, filter_len):
      cpu_filter, _ = scipy.signal.butter(filter_len, 0.5)
      gpu_filter = cupy.asarray(cpu_filter, dtype=dtype)
      gpu_output = cupyx.signal.firfilter_zi(gpu_filter)
      cpu_output = scipy.signal.lfilter_zi(cpu_filter, 1.0)
      # Values are big so a big atol is ok
      testing.assert_allclose(gpu_output, cpu_output, atol=5e-1)
      assert cupy.real(gpu_output).dtype == dtype
  
file_path: cupy/tests/cupyx_tests/signal_tests/filtering_tests/test_filtering.py
imports: import pytest
  import numpy
  import scipy
  import cupy
  import cupyx.signal
  import cupyx.scipy.signal
  from cupy import testing
label_desc: Use image node_id 3 for calling a global function with example usage: test_firfilter_zi(dtype, filter_len) without return types