@classmethod
def _join(cls, text):
    """Convert single newlines (ignored by Markdown) to spaces.

        >>> Markdown._join("abc\\n123")
        'abc 123'

        >>> Markdown._join("abc\\n\\n123")
        'abc\\n\\n123'

        >>> Markdown._join("abc \\n123")
        'abc 123'

        """
    return cls.REGEX_MARKDOWN_SPACES.sub('\\1 \\3', text).strip()
