Combine terms with AND.
        There must be a term added before using this method.

        Arguments:
            close_group (bool): If ``True``, will end the current group and start a new one.
                    If ``False``, will continue current group.

                    Example::

                        If the current query is "(term1"
                        .and(close_group=True) => "(term1) AND ("
                        .and(close_group=False) => "(term1 AND "

        Returns:
            SearchHelper: Self

def _and_join(self, close_group=False):
        """Combine terms with AND.
        There must be a term added before using this method.

        Arguments:
            close_group (bool): If ``True``, will end the current group and start a new one.
                    If ``False``, will continue current group.

                    Example::

                        If the current query is "(term1"
                        .and(close_group=True) => "(term1) AND ("
                        .and(close_group=False) => "(term1 AND "

        Returns:
            SearchHelper: Self
        """
        if not self.initialized:
            raise ValueError("You must add a search term before adding an operator.")
        else:
            self._operator("AND", close_group=close_group)
        return self