code: def _infer_column_defaults(
      filenames,
      num_cols,
      field_delim,
      use_quote_delim,
      na_value,
      header,
      num_rows_for_inference,
      select_columns,
      file_io_fn,
  ):
      """Infers column types from the first N valid CSV records of files."""
      if select_columns is None:
          select_columns = range(num_cols)
      inferred_types = [None] * len(select_columns)
  
      for i, csv_row in enumerate(
          _next_csv_row(
              filenames,
              num_cols,
              field_delim,
              use_quote_delim,
              header,
              file_io_fn,
          )
      ):
          if (
              num_rows_for_inference is not None
              and i >= num_rows_for_inference
          ):
              break
  
          for j, col_index in enumerate(select_columns):
              inferred_types[j] = _infer_type(
                  csv_row[col_index], na_value, inferred_types[j]
              )
  
      # Replace None's with a default type
      inferred_types = [t or dtypes.string for t in inferred_types]
      # Default to 0 or '' for null values
      return [
          constant_op.constant(
              [0 if t is not dtypes.string else ""], dtype=t
          )
          for t in inferred_types
      ]
  
imports: import collections
  import csv
  import functools
  import gzip
  import numpy
  from tensorflow.python import tf2
  from tensorflow.python.compat import v2_compat
  from tensorflow.python.data.experimental.ops import error_ops
  from tensorflow.python.data.experimental.ops import parsing_ops
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.data.ops import map_op
  from tensorflow.python.data.ops import options
  from tensorflow.python.data.ops import readers
  from tensorflow.python.data.util import convert
  from tensorflow.python.data.util import nest
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_spec
  from tensorflow.python.framework import tensor_util
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.ops import gen_experimental_dataset_ops
  from tensorflow.python.ops import io_ops
  from tensorflow.python.platform import gfile
  from tensorflow.python.util.tf_export import tf_export
label_desc: Use image node_id 6 for calling a global function with example usage: _infer_column_defaults(filenames, num_cols, field_delim, use_quote_delim, na_value, header, num_rows_for_inference, select_columns, file_io_fn) and returns: unknown