code: def remove_extra_empty_lines(self, input_model):
          
          ncnt = 0
          output_model = []
          for ln in input_model:
              if ln[0].strip(' \n\r') is '':
                  if ncnt is 0:
                      output_model.append(ln)
                  elif self.debug_level > 1:
                          self.debug_print_strip_msg(ln[1] - 1, ln[0])
                  ncnt += 1
              else:
                  output_model.append(ln)
                  ncnt = 0
          if self.debug_level > 0:
              print('   Removed %d empty lines' % (len(input_model) - len(output_model)))
          return output_model
docs: Removes superfluous newlines from a YANG model that was extracted
          from a draft or RFC text. Newlines are removed whenever 2 or more
          consecutive empty lines are found in the model. This function is a
          part of the model post-processing pipeline.
          :param input_model: The YANG model to be processed
          :return: YANG model with superfluous newlines removed