code: def embed_coords(self, coords):
      # Fill up a triangular matrix, pad it with zeros and then copy it to the
      # other side. We'll assume the diagonal has zeros.
      n = int((-1 + np.sqrt(1 + 8 * self.dims)) / 2) + 1
      matrices = linalg.fill_triangular(coords)
      matrices_shape = tf.shape(matrices)
      row_shape = tf.concat([matrices_shape[:-2], [1, n - 1]], axis=0)
      matrices = tf.concat(
          [tf.zeros(row_shape, dtype=coords.dtype), matrices], axis=-2
      )
      col_shape = tf.concat([matrices_shape[:-2], [n, 1]], axis=0)
      matrices = tf.concat(
          [matrices, tf.zeros(col_shape, dtype=coords.dtype)], axis=-1
      )
      matrices = tf.linalg.matrix_transpose(matrices) + matrices
      return matrices
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import exp
  from tensorflow_probability.python.bijectors import reshape
  from tensorflow_probability.python.bijectors import scale
  from tensorflow_probability.python.experimental.tangent_spaces import spaces_test_util
  from tensorflow_probability.python.experimental.tangent_spaces import symmetric_matrix
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import linalg
label_desc: Use image node_id 2 for calling the _ConstantDiagonalSymmetricMatrixTest obj's underlying member method code with example usage: obj.embed_coords(coords) and returns: matrices