code: def filelist_prune(self, at_data, *args, **kwargs):
          
  
          b_status    = True
          l_file      = []
          str_path    = at_data[0]
          al_file     = at_data[1]
          if len(self.str_extension):
              al_file = [x for x in al_file if self.str_extension in x]
  
          if len(al_file):
              al_file.sort()
              l_file      = al_file
              b_status    = True
          else:
              self.dp.qprint( "No valid files to analyze found in path %s!" % str_path, 
                              comms = 'error', level = 3)
              l_file      = None
              b_status    = False
          return {
              'status':   b_status,
              'l_file':   l_file
          }
docs: Given a list of files, possibly prune list by 
          extension.