code: def input_joint_matrix(self):
      if self.use_histogram:
          return self.approx.joint_histogram
      else:
          return self.approx.symbolic_random
  
file_path: pymc/pymc/variational/stein.py
imports: import pytensor.tensor
  from pytensor.graph.replace import graph_replace
  from pymc.pytensorf import floatX
  from pymc.util import WithMemoization, locally_cachedmethod
  from pymc.variational.opvi import node_property
  from pymc.variational.test_functions import rbf
label_desc: Use image node_id 2 for calling the Stein obj's underlying member method code with example usage: obj.input_joint_matrix() and returns: self, self