如何在一个主题中只保留一个参数？

def print_theme(theme='default'):
    print(f"The current theme is {theme}.")

print_theme()  # 输出：The current theme is default.
print_theme('dark')  # 输出：The current theme is dark.

def set_theme_style(theme_style):
    # 根据字典中的键值对进行相应的操作
    if 'background_color' in theme_style:
        # 设置背景颜色
        print(f"Setting background color to {theme_style['background_color']}.")
    if 'font_color' in theme_style:
        # 设置字体颜色
        print(f"Setting font color to {theme_style['font_color']}.")

theme_style = {'background_color': 'white', 'font_color': 'black'}
set_theme_style(theme_style)
# 输出：
# Setting background color to white.
# Setting font color to black.

class ThemeManager:
    def __init__(self, theme='default'):
        self.theme = theme
    
    def set_theme(self):
        print(f"Setting theme to {self.theme}.")
    
    def apply_theme(self):
        print(f"Applying theme: {self.theme}.")

theme_manager = ThemeManager('dark')
theme_manager.set_theme()  # 输出：Setting theme to dark.
theme_manager.apply_theme()  # 输出：Applying theme: dark.