Seems that cannot bold the parentheses symbols (, )，or operator symbols like +, -, = in formulas

[xiezhenjian]

I tried \bm command，but not work。
For example，when I tried to render \bm{f(x)=1}，symbols f, x, 1 was bold，but (, ), = not。
Is this feature currently not supported ?
Or Is there any other way to solve this bold problem？