code: def add_section(self, section, comment=None):
          
          self._read_sources()
  
          if self._to_dot_key(section) in self._dot_keys:
              raise DuplicateSectionError(section)
  
          self._parser.add_section(section)
          self._add_dot_key(section)
          if comment:
              self._set_comment(section, comment)
docs: Add a section
  
          :param str section: Section to add
          :raise DuplicateSectionError: if section already exist.