def gradient_summand(weights, lp):
    """Calculates the gradient summand for a given weight and `LabeledPoint`.

    Note:
        `DenseVector` behaves similarly to a `numpy.ndarray` and they can be used interchangably
        within this function.  For example, they both implement the `dot` method.

    Args:
        weights (DenseVector): An array of model weights (betas).
        lp (LabeledPoint): The `LabeledPoint` for a single observation.

    Returns:
        DenseVector: An array of values the same length as `weights`.  The gradient summand.
    """
    return (weights.dot(lp.features) - lp.label) * lp.features