<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def pre_script(self):
 """ execute the pre script if it is defined """

        if self['pre_script'] is None:
            return
        LOGGER.info("Executing pre script: {}".format(self['pre_script']))
        cmd = self['pre_script']
        execute_command(self.abs_input_dir(), cmd, self.env_dictionary())
        LOGGER.info("Pre Script completed")