code: def test_validation(self):
      def _check_is_not_nan(x: float) -> float:
          if math.isnan(x):
              raise ValueError("Must not be NAN")
          return x
  
      float_flag_def = flag_def.SingleValueFlagDef(
          name="value",
          parse_type=float,
          parse_to_dest_type_fn=_check_is_not_nan,
          required=True,
      )
  
      results = _new_parser(float_flag_def).parse_args(
          ["--value", "0.25"]
      )
      self.assertEqual(0.25, results.value)
  
      with self.assertRaisesRegex(
          argument_parser.ParserError, "Must not be NAN"
      ):
          _new_parser(float_flag_def).parse_args(["--value", "nan"])
  
imports: from __future__ import annotations
  import argparse
  import enum
  import math
  from absl.testing import absltest
  from google.generativeai.notebook import argument_parser
  from google.generativeai.notebook import flag_def
label_desc: Use image node_id 7 for calling the SingleValueFlagDefTest obj's underlying member method code with example usage: obj.test_validation() and returns: x