def _analyze(self):
if self.value is None or self.value == self.previous:<EOL><INDENT>pass<EOL><DEDENT>elif self._operation == "<STR_LIT>":<EOL><INDENT>self._additions = self.value<EOL><DEDENT>elif self._operation == "<STR_LIT>":<EOL><INDENT>self._removals = self.value<EOL><DEDENT>elif self.previous is None:<EOL><INDENT>self._assignments = self.value<EOL><DEDENT>else:<EOL><INDENT>self._additions = (self.value - self.previous) or None<EOL>self._removals = (self.previous - self.value) or None<EOL><DEDENT>self._analyzed = True<EOL>
works out the updates to be performed