def predict_on_patch(patch, model, patch_size=256):
    """Predict pixel level probabilites of being a tumor of a single patch.

    Parameters
    ----------
    patch: array_like
           RGB patch
    model: Keras model
           as obtained from get_model

    Returns
    -------
    prediction: array_like
                patch_size x patch_size x 1  per-pixel tumor probability
    """
    prediction = model.predict(patch.reshape(1, patch_size, patch_size, 3))
    prediction = prediction[:, :, :, 1].reshape(patch_size, patch_size)
    return prediction