code: def ppf(x, n):
      try:
          from scipy import stats
      except ImportError:
          stats = None
  
      if stats:
          if n < 30:
              return stats.t.ppf(x, n)
          return stats.norm.ppf(x)
      else:
          if n < 30:
              # TODO: implement power series:
              # http://eprints.maths.ox.ac.uk/184/1/tdist.pdf
              raise ImportError(
                  "You must have scipy installed to use t-student "
                  "when sample_size is below 30"
              )
          return norm_ppf(x)
  
imports: from math import log, pi, sqrt
label_desc: Use image node_id 3 for calling a global function with example usage: ppf(x, n) and returns: stats, norm_ppf, stats