<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def print_diff(self, summary1=None, summary2=None):
 """Compute diff between to summaries and print it. If no summary is provided, the diff from the last to the current summary is used. If summary1 is provided the diff from summary1 to the current summary is used. If summary1 and summary2 are provided, the diff between these two is used. """

        summary.print_(self.diff(summary1=summary1, summary2=summary2))