code: def qlognormal_lpdf(x, mu, sigma, q):
      # casting rounds up to nearest step multiple.
      # so lpdf is log of integral from x-step to x+1 of P(x)
  
      # XXX: subtracting two numbers potentially very close together.
      return np.log(
          lognormal_cdf(x, mu, sigma) - lognormal_cdf(x - q, mu, sigma)
      )
  
imports: import logging
  import time
  import numpy
  from scipy.special import erf
  from .None import pyll
  from .pyll import scope
  from .pyll.stochastic import implicit_stochastic
  from .base import miscs_to_idxs_vals
  from .base import miscs_update_idxs_vals
  from .None import rand
label_desc: Use image node_id 9 for calling a global function with example usage: qlognormal_lpdf(x, mu, sigma, q) and returns: np