How to use the mailmerge.utils function in mailmerge

raise utils.MailmergeError("Empty attachment header.")

        # Create a Path object and handle home directory (tilde ~) notation
        path = Path(path.strip())
        path = path.expanduser()

        # Relative paths are relative to the template's parent dir
        if not path.is_absolute():
            path = self.template_path.parent/path

        # Resolve any symlinks
        path = path.resolve()

        # Check that the attachment exists
        if not path.exists():
            raise utils.MailmergeError("Attachment not found: {}".format(path))

        return path

def _resolve_attachment_path(self, path):
        """Find attachment file or raise MailmergeError."""
        # Error on empty path
        if not path.strip():
            raise utils.MailmergeError("Empty attachment header.")

        # Create a Path object and handle home directory (tilde ~) notation
        path = Path(path.strip())
        path = path.expanduser()

        # Relative paths are relative to the template's parent dir
        if not path.is_absolute():
            path = self.template_path.parent/path

        # Resolve any symlinks
        path = path.resolve()

        # Check that the attachment exists
        if not path.exists():
            raise utils.MailmergeError("Attachment not found: {}".format(path))