text: class Parser:
      """
      Parser of commands
      """
  
      @staticmethod
      def parse_file(filename):
          """Parse commands from a file."""
          with open(filename, 'r') as f:
              content = f.read()
          return Parser.parse_content(content)
  
      @staticmethod
      def parse_content(content):
          """Parse commands from a multi-line string."""
          lines = content.split('\n')
          commands = []
          for line in lines:
              command = Parser.parse_command(line)
              if command:
                  commands.append(command)
          return commands
  
      @staticmethod
      def parse_command(command):
          """Parse command from a single-line string."""
          command = command.rstrip('\n')
          if Parser.is_empty(command):
              return None
          return command
  
      @staticmethod
      def is_empty(command):
          """Check if a string is an empty command."""
          return str.isspace(command)
  