def price_derivative(tf_price, tf_session,
                     params
                    ):
  """Wrapper executing the computation graph for a given derivative.

  Args:
    tf_price: a tensorflow tensor corresponding to the derivative's price
      estimate.
    tf_session: a tensorflow session which will execute the graph.
    params: a dictionary {placeholder: value} that will be fed into the session.

  Returns:
    A scalar estimating the derivative's price.
  """
  return tf_session.run(tf_price, feed_dict=params)