<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def fix_e231(self, result):
 """Add missing whitespace."""

        line_index = result['line'] - 1
        target = self.source[line_index]
        offset = result['column']
        fixed = target[:offset].rstrip() + ' ' + target[offset:].lstrip()
        self.source[line_index] = fixed