code: def _find_only_column_of_type(
      sframe, target_type, type_name, col_name
  ):
      """
      Finds the only column in `SFrame` with a type specified by `target_type`.
      If there are zero or more than one such columns, an exception will be
      raised. The name and type of the target column should be provided as
      strings for the purpose of error feedback.
      """
      image_column_name = None
      if type(target_type) != list:
          target_type = [target_type]
      for name, ctype in zip(
          sframe.column_names(), sframe.column_types()
      ):
          if ctype in target_type:
              if image_column_name is not None:
                  raise ToolkitError(
                      'No "{col_name}" column specified and more than one {type_name} column in "dataset". Can not infer correct {col_name} column.'.format(
                          col_name=col_name, type_name=type_name
                      )
                  )
              image_column_name = name
      if image_column_name is None:
          raise ToolkitError(
              'No "{col_name}" column specified and no column with expected type "{type_name}" is found.'.format(
                  col_name=col_name, type_name=type_name
              )
              + ' "datasets" consists of columns with types: '
              + ", ".join([x.__name__ for x in sframe.column_types()])
              + "."
          )
      return image_column_name
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  from ..data_structures.sframe import SArray
  from ..data_structures.sframe import SFrame
  from ..data_structures.sgraph import SGraph
  from ..data_structures.sgraph import Vertex
  from ..data_structures.sgraph import Edge
  from .._cython.cy_sarray import UnitySArrayProxy
  from .._cython.cy_sframe import UnitySFrameProxy
  from .._cython.cy_graph import UnityGraphProxy
  from ..toolkits._main import ToolkitError
  import json
  import six
label_desc: Use image node_id 3 for calling a global function with example usage: _find_only_column_of_type(sframe, target_type, type_name, col_name) and returns: image_column_name