class_docstr: Logatithm Normal Distribution.
  
  The probability density function of the distribution is expressed as
  
  .. math::
      p(x;\mu,\sigma) = \frac{1}{\sqrt{2\pi\sigma^2}x}
          \exp\left(-\frac{(\log{x}-\mu)^2}{2\sigma^2}\right)
  
  Args:
      mu(:class:`~chainer.Variable` or :ref:`ndarray`): Parameter of
          distribution :math:`\mu`.
      sigma(:class:`~chainer.Variable` or :ref:`ndarray`): Parameter of
          distribution :math:`\sigma`.
code: def mu(self):
      return chainer.as_variable(self.__mu)
  
imports: import math
  import chainer
  from chainer import backend
  from chainer.backends import cuda
  from chainer import distribution
  from chainer.functions.math import exponential
  from chainer.utils import cache
label_desc: Use image node_id 2 for calling the LogNormal obj's underlying member method code with example usage: obj.mu() and returns: chainer