code: def run_bandwidth_test(ddf, n):
      df, time_ls = get_n_rows(ddf, n)
      time_ar = np.asarray(time_ls)
      time_mean = time_ar.mean()
      size_bytes = df.memory_usage().sum()
      size_gb = round(size_bytes / (pow(1024, 3)), 2)
      print(
          f"Getting {len(df):,} rows  of size {size_gb} took = {time_mean*1e-6} ms"
      )
      time_mean_s = time_mean * 1e-9
      print(f"Bandwidth = {round(size_gb/time_mean_s, 4)} gb/s")
      return
  
file_path: cugraph/benchmarks/shared/build_cugraph_ucx/test_client_bandwidth.py
imports: from dask_cuda import LocalCUDACluster
  from dask.distributed import Client, wait
  import cupy
  import numpy
  import cudf
  import dask_cudf
  import rmm
  from time import perf_counter_ns
label_desc: Use image node_id 4 for calling a global function with example usage: run_bandwidth_test(ddf, n) without return types