<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def diff_files(left, right, diff_options=None, formatter=None):
 """Takes two filenames or streams, and diffs the XML in those files"""

    return _diff(etree.parse, left, right,
                 diff_options=diff_options, formatter=formatter)