code: def d_plus(
      tau: types.FloatTensor,
      z: types.FloatTensor,
      r: types.FloatTensor,
      q: types.FloatTensor,
      sigma: types.FloatTensor,
  ) -> types.FloatTensor:
      dtype = tau.dtype
      epsilon = machine_eps(dtype)
      return (
          tf.math.log(tf.math.maximum(z, epsilon))
          + (r - q + 0.5 * sigma**2) * tau
      ) / (sigma * tf.math.sqrt(tau) + epsilon)
  
file_path: tf-quant-finance/tf_quant_finance/experimental/american_option_pricing/common.py
imports: import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.internal import dtype_util
  from tf_quant_finance import types
label_desc: Use image node_id 2 for calling a global function with example usage: d_plus(tau, z, r, q, sigma) and returns: unknown