def read(self, given_file):
        if self.unique is not False and self.unique is not True:
            raise AttributeError("Attribute 'unique' is not True or False.")
        self.filename = str.strip(given_file)
        self.log('Read-only opening {0}'.format(self.filename))
        with open(self.filename, 'r') as handle:
            for line in handle:
                line = line.rstrip('\r\n')
                if line is None:
                    line = ''
                if self.unique is False or line not in self.contents:
                    self.contents.append(line)
        if self.sorted:
            self.sort()
        self.log('Read {0} lines.'.format(len(self.contents)))
        return True