'Check for the existence of a given option in a given section.'

def has_option(self, section, option):

    if ((not section) or (section == DEFAULTSECT)):
        option = self.optionxform(option)
        return (option in self._defaults)
    else:
        if (section not in self._sections):
            return False
        option = self.optionxform(option)
        return ((option in self._sections[section]) or (option in self._defaults))
