class_docstr: Sparse GP regression.
  
  The key reference is :cite:t:`titsias2009variational`.
  
  For a use example see :doc:`../../../../notebooks/getting_started/large_data`.
docstr: :param common: A named tuple containing matrices that will be used
  :return: Lower bound on -.5 yᵀ(K + σ²I)⁻¹y
docstr_tok: [":","param","common",":","A","named","tuple","containing","matrices","that","will","be","used",":","return",":","Lower","bound","on","-.5","y\u1d40","(","K","+","\u03c3\u00b2I",")","\u207b\u00b9y"]
code: def quad_term(self, common: "SGPR.CommonTensors") -> tf.Tensor:
      """
      :param common: A named tuple containing matrices that will be used
      :return: Lower bound on -.5 yᵀ(K + σ²I)⁻¹y
      """
      sigma = common.sigma
      A = common.A
      LB = common.LB
  
      x, y = self.data
      err = (y - self.mean_function(x)) / sigma[..., None]
  
      Aerr = tf.linalg.matmul(A, err)
      c = tf.linalg.triangular_solve(LB, Aerr, lower=True)
  
      # σ⁻² yᵀy
      err_inner_prod = tf.reduce_sum(tf.square(err))
      c_inner_prod = tf.reduce_sum(tf.square(c))
  
      quad = -0.5 * (err_inner_prod - c_inner_prod)
      return quad
  
imports: from typing import NamedTuple, Optional, Tuple
  import numpy
  import tensorflow
  from check_shapes import check_shapes, inherit_check_shapes
  from ..None import posteriors
  from ..base import InputData, MeanAndVariance, RegressionData, TensorData
  from ..config import default_float, default_jitter
  from ..covariances.dispatch import Kuf, Kuu
  from ..inducing_variables import InducingPoints
  from ..kernels import Kernel
  from ..likelihoods import Gaussian
  from ..mean_functions import MeanFunction
  from ..utilities import add_noise_cov, assert_params_false, to_default_float
  from .model import GPModel
  from .training_mixins import InternalDataTrainingLossMixin
  from .util import InducingPointsLike, data_input_to_tensor, inducingpoint_wrapper
label_desc: Use image node_id 4 for calling the SGPR_deprecated obj's underlying member method code with example usage: obj.quad_term(common) and returns: quad