code: def test_constant_fwd_interpolation(self):
      curve = build_cuve(
          interpolation_method=InterpolationMethod.CONSTANT_FORWARD
      )
      start_dates = [
          (2020, 7, 18),
          (2020, 8, 18),
          (2020, 8, 18),
          (2025, 1, 1),
      ]
      maturity_dates = [
          (2020, 7, 19),
          (2020, 8, 19),
          (2020, 12, 18),
          (2025, 3, 1),
      ]
      values = self.evaluate(
          curve.forward_rate(
              start_date=start_dates, maturity_date=maturity_dates
          )
      )
      np.testing.assert_allclose(
          values,
          [0.0512969, 0.0512969, 0.05173552, 0.05290519],
          atol=1e-6,
      )
  
file_path: tf-quant-finance/tf_quant_finance/experimental/pricing_platform/framework/market_data/rate_curve_test.py
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  import tf_quant_finance
  from tensorflow.python.framework import test_util
label_desc: Use image node_id 6 for calling the RateCurveTest obj's underlying member method code with example usage: obj.test_constant_fwd_interpolation() without return types