def __init__(self, qtol, qmax=None, max_iter=None):
if qtol is None:<EOL><INDENT>raise ValueError("<STR_LIT>")<EOL><DEDENT>self.qtol = qtol<EOL>self.max_iter = max_iter<EOL>LineSearch.__init__(self, qmax)<EOL>self.num_bracket = <NUM_LIT:0><EOL>self.num_golden = <NUM_LIT:0><EOL>
Argument:
 | ``qtol``  --  The threshold for displacements along the line.
                 (When displacements become smaller than qtol, we
                 assume convergence.)
Optional arguments
 | ``qmax``  --  The maximum step size of a line search
 | ``max_iter``  --  the maximum number of iteration for the line
                     search (only applies to the bracketing part)