Clear the terminal screen.

def clear(self):
        """
        Clear the terminal screen.
        """
        if hasattr(self.stdout, 'isatty') and self.stdout.isatty() or self.term_type == 'mintty':
            cmd, shell = {
                'posix': ('clear', False),
                'nt': ('cls', True),
                'cygwin': (['echo', '-en', r'\ec'], False),
                'mintty': (r'echo -en "\ec', False),
            }[self.term_type]
            subprocess.call(cmd, shell=shell, stdin=self.stdin, stdout=self.stdout, stderr=self.stderr)