def _find_end_token(self, end_token, operation):
        """Looks for a statement in the operation's list that matches the specified
        end token. Returns the index of the statement in the operation that matches.
        """
        ibuffer, icache = operation.state
        length = operation.buffered[ibuffer][2]
        result = None

        for i in range(len(operation.buffered) - ibuffer - 1):
            linenum, statement, charlength = operation.buffered[i + ibuffer + 1]
            length += charlength
            
            if end_token in statement.lower():
                #We already have the absolute char index for the start of the
                #instance; we just need to update the end.
                result = (i + ibuffer + 1, length)
                break        

        #If we didn't find a terminating statement, the full length of the operation
        #is a good estimate for the extent of the instance.
        if result is None:
            result = (None, length)

        return result
Looks for a statement in the operation's list that matches the specified
        end token. Returns the index of the statement in the operation that matches.