def dabs(self, x):
if x < <NUM_LIT:0>:<EOL><INDENT>return -<NUM_LIT:1.><EOL><DEDENT>elif x > <NUM_LIT:0>:<EOL><INDENT>return <NUM_LIT:1.><EOL><DEDENT>else:<EOL><INDENT>return <NUM_LIT:0.><EOL><DEDENT>
derivative of absolute value