code: def _validate_fetch(graph, fetch):
      try:
          fetch_t = graph.as_graph_element(
              fetch, allow_tensor=True, allow_operation=True
          )
          # For now, do not make a difference between a subfetch and a target
          return fetch_t.name
      except TypeError as e:
          raise TypeError(
              "Fetch argument %r has invalid type %r, "
              "must be a string or Tensor. (%s)"
              % (fetch, type(fetch), str(e))
          )
      except ValueError as e:
          raise ValueError(
              "Fetch argument %r cannot be interpreted as a "
              "Tensor. (%s)" % (fetch, str(e))
          )
      except KeyError as e:
          raise ValueError(
              "Fetch argument %r cannot be interpreted as a "
              "Tensor. (%s)" % (fetch, str(e))
          )
  
imports: import tensorflow
  import numpy
  import logging
  import tempfile
  import pandas
  from pyspark import RDD, SparkContext
  from pyspark.sql import SQLContext, Row, DataFrame
  from pyspark.sql.types import DoubleType, IntegerType, LongType, FloatType, ArrayType
label_desc: Use image node_id 27 for calling a global function with example usage: _validate_fetch(graph, fetch) and returns: fetch_t