def _transform_positioning(ha, va):
    """Converts matplotlib positioning to pgf node positioning.
    Not quite accurate but the results are equivalent more or less."""
    if ha == 'center' and va == 'center':
        return None
    ha_mpl_to_tikz = {'right': 'east', 'left': 'west', 'center': ''}
    va_mpl_to_tikz = {'top': 'north', 'bottom': 'south', 'center': '',
        'baseline': 'base'}
    return 'anchor={} {}'.format(va_mpl_to_tikz[va], ha_mpl_to_tikz[ha]).strip(
        )
