def get_output_dim_for_mixture(mixture_components=20):
    """
    for mixture_componenets = 20
    output dimension is (20 weights, 40 means, 40 standard deviations
      and 20 correlations) + 1 end-of-stroke
    output_dim = 121 = 6 * mixture_components + 1
    """
    return mixture_components * 6 + 1