code: def is_code(filename):
      
      with open(filename, "r") as file:
          for line in file:
              # ignore comments and empty lines
              if not is_comment(line) \
                      and '{' in line: # <-- simple indicator for code
                  if '${' not in line: # <-- ${abc} variable to substitute
                      return True
      return False
docs: This function returns True, if  a line of the file contains bracket '{'.