'Evaluate each line of ``lines`` with the ``Environment`` environment, returning
the value of the last line.'

def wkf_expr_eval_expr(self, lines):

    assert lines, 'You    used    a    NULL    action    in    a    workflow,    use    dummy    node    instead.'
    result = False
    for line in lines.split('\n'):
        line = line.strip()
        if (not line):
            continue
        if (line == 'True'):
            result = True
        elif (line == 'False'):
            result = False
        else:
            env = Environment(self.session, self.record)
            result = safe_eval(line, env, nocopy=True)
    return result
