def has_false(self, e, extra_constraints=(), solver=None, model_callback=None): 
<EOL>return self._has_false(self.convert(e), extra_constraints=extra_constraints, solver=solver, model_callback=model_callback)<EOL>
Should return False if `e` can possibly be False.

:param e:                   The AST.
:param extra_constraints:   Extra constraints (as ASTs) to add to the solver for this solve.
:param solver:              A solver, for backends that require it.
:param model_callback:      a function that will be executed with recovered models (if any)
:return:                   A boolean.