code: def get_notmuch_setting(self, section, key, fallback=None):
          
          value = None
          if section in self._notmuchconfig:
              if key in self._notmuchconfig[section]:
                  value = self._notmuchconfig[section][key]
          if value is None:
              value = fallback
          return value
docs: look up config values from notmuch's config
  
          :param section: key is in
          :type section: str
          :param key: key to look up
          :type key: str
          :param fallback: fallback returned if key is not present
          :type fallback: str
          :returns: config value with type as specified in the spec-file