### absolute value for the ln function

I tried to execute this but could not figure out the absolute value sign correctly

$c = var('c')$

$c=-0.999$

$(sqrt(1-c^2)/Pi)*[2.239539+(c/sqrt(1-c^2))*ln|(0.9*sqrt(1-c^2)-c*0.435889)/(0.9*sqrt(1-c^2)+c*0.435889)|+(1.8*sqrt(0.19)/(0.81-c^2)]$

I need help on the correct symbol for the absolute value for the ln function.