code: def to_db_func(multiplier, reference, cutoff_db, input_data):
      if not reference:
          reference = np.amax(input_data)
      min_ratio = 10 ** (cutoff_db / multiplier)
      out = multiplier * np.log10(
          np.maximum(min_ratio, input_data / reference)
      )
      return out
  
imports: from nvidia.dali.pipeline import Pipeline
  import nvidia.dali.ops
  import numpy
  from functools import partial
  from test_utils import compare_pipelines
  from test_utils import RandomDataIterator
  from nose_utils import raises
label_desc: Use image node_id 1 for calling a global function with example usage: to_db_func(multiplier, reference, cutoff_db, input_data) and returns: out