code: def testUnknownInputRankError(self):
      # Use a tf.function that erases shape information.
      @def_function.function(
          input_signature=[tensor_spec.TensorSpec(None)]
      )
      def f(v):
          return ragged_string_ops.unicode_encode(v, "UTF-8")
  
      with self.assertRaisesRegex(
          ValueError, "Rank of input_tensor must be statically known."
      ):
          f([72, 101, 108, 108, 111])
  
imports: from absl.testing import parameterized
  import numpy
  from tensorflow.python.eager import def_function
  from tensorflow.python.framework import constant_op
  from tensorflow.python.framework import errors_impl
  from tensorflow.python.framework import tensor_spec
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops.ragged import ragged_factory_ops
  from tensorflow.python.ops.ragged import ragged_string_ops
  from tensorflow.python.ops.ragged import ragged_tensor
  from tensorflow.python.ops.ragged import ragged_tensor_value
  from tensorflow.python.platform import test
label_desc: Use image node_id 17 for calling the UnicodeEncodeOpTest obj's underlying member method code with example usage: obj.testUnknownInputRankError() and returns: ragged_string_ops