human
Solve the following python programming problem given the following code:
def refresh_style(self) : 
    ' Refresh the theme styling for the widget.

        This method will style the widget and the lexer using the
        current theme that was provided by the declaration object.

        ' 
    colorcache = { 
        
} 
    fontcache = { 
        
} 
    def get_color(color_str) : 
        if (color_str in colorcache) : 
            return colorcache [color_str] 
color = colorcache [color_str] = _make_color (color_str) 
        return color 
def get_font(font_str) : 
        if (font_str in fontcache) : 
            return fontcache [font_str] 
font = fontcache [font_str] = _make_font (font_str) 
        return font 
def pull_color(dct, key, default) : 
        color = dct.get (key) 
        if (color is None) : 
            return default 
return get_color (color) 
def pull_font(dct, key, default) : 
        font = dct.get (key) 
        if (font is None) : 
            return default 
return get_font (font) 
caret_color = QColor (0, 0, 0) 
    default_color = QColor (0, 0, 0) 
    default_paper = QColor (255, 255, 255) 
    default_font = QFont () 
    theme = self.declaration.theme 
    settings = theme.get ('settings') 
    if (settings is not None) : 
        caret_color = pull_color (settings, 'caret', caret_color) 
        default_color = pull_color (settings, 'color', default_color) 
        default_paper = pull_color (settings, 'paper', default_paper) 
        default_font = pull_font (settings, 'font', default_font) 
widget = self.widget 
    widget.setCaretForegroundColor (caret_color) 
    widget.setColor (default_color) 
    widget.setPaper (default_paper) 
    widget.setFont (default_font) 
    lexer = widget.lexer () 
    if (lexer is None) : 
        return 
syntax = LEXERS_INV.get (type (lexer)) 
    if (syntax is None) : 
        return 
syntax_rules = theme.get (syntax, { 
        
}) 
    syntax_tokens = TOKENS.get (syntax, { 
        
}) 
    syntax_default = syntax_rules.get ('default', { 
        
}) 
    default_color = pull_color (syntax_default,...

    
    

    Fix the buggy line: if (lexer is not None) :
assistant
#Here is Python program to fix the buggy line: if (lexer is not None) :
.

if (qtoken is not None) :