docs: def postcode_in_state(self, state_abbr=None):
          """
          :example '4703'
          """
          if state_abbr is None:
              state_abbr = self.random_element(self.states_abbr)
  
          if state_abbr in self.states_abbr:
              postcode = "%d" % (self.generator.random.randint(
                              self.states_postcode[state_abbr][0],
                              self.states_postcode[state_abbr][1]))
  
              if len(postcode) == 3:
                  postcode = "0%s" % postcode
  
              return postcode
  
          else:
              raise Exception('State Abbreviation not found in list')