The coefficient of \( x^{256} \) in the expansion of \( (1-x)^{101}\left(x^{2}+x+1\right)^{100} \) is:
\( {}^{100}C_{16} \)
\( {}^{100}C_{15} \)
\( -{}^{100}C_{15} \)
\( -{}^{100}C_{16} \)