class_docstr: Exponential Distribution 
class_docstr_tok: ["Exponential","Distribution"]
docstr: Returns value of pdf at x 
docstr_tok: ["Returns","value","of","pdf","at","x"]
code: def pdf(self, x):
      """Returns value of pdf at x"""
      if x < 0:
          return 0
      return np.asscalar(self.lam * np.exp(-self.lam * x))
  
imports: from __future__ import absolute_import
  from __future__ import division
  import numpy
  from .distribution import Continuous
  from ..exd import domains
label_desc: Use image node_id 2 for calling the Exponential obj's underlying member method code with example usage: obj.pdf(x) and returns: np, int