<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def save_csv(self, fd):
 """ Saves the case as a series of Comma-Separated Values. """

        from pylon.io.excel import CSVWriter
        CSVWriter(self).write(fd)