code: def get_data_source_registry():
      """Get the global data source registry. If the registry is empty,
      initialize the registry with predefined data sources."""
      global _data_source_registry
      if not _data_source_registry.list():
          _init_data_source_registry(_data_source_registry)
      return _data_source_registry
  
file_path: io/tests/test_atds_avro/utils/data_source_registry.py
imports: from enum import Enum
  import numpy
  import tensorflow
  from tensorflow.python.framework import registry
  from tests.test_atds_avro.utils.data_source import DataSource
  from tests.test_atds_avro.utils.generator.tensor_generator import IntTensorGenerator, FloatTensorGenerator, WordTensorGenerator, BoolTensorGenerator
  from tests.test_atds_avro.utils.generator.sparse_tensor_generator import IntSparseTensorGenerator, FloatSparseTensorGenerator, WordSparseTensorGenerator, BoolSparseTensorGenerator, ValueDistribution
  from tests.test_atds_avro.utils.generator.varlen_tensor_generator import DimensionDistribution, IntVarLenTensorGenerator, FloatVarLenTensorGenerator, WordVarLenTensorGenerator, BoolVarLenTensorGenerator, DIM_DISTRIBUTION_TO_RANGE
label_desc: Use image node_id 2 for calling a global function with example usage: get_data_source_registry() and returns: _data_source_registry