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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def scatter_group(ax, key, imask, adata, Y, projection='2d', size=3, alpha=None):
 """Scatter of group using representation of data Y. """

    mask = adata.obs[key].cat.categories[imask] == adata.obs[key].values
    color = adata.uns[key + '_colors'][imask]
    if not isinstance(color[0], str):
        from matplotlib.colors import rgb2hex
        color = rgb2hex(adata.uns[key + '_colors'][imask])
    if not is_color_like(color):
        raise ValueError('"{}" is not a valid matplotlib color.'.format(color))
    data = [Y[mask, 0], Y[mask, 1]]
    if projection == '3d': data.append(Y[mask, 2])
    ax.scatter(*data,
               marker='.',
               alpha=alpha,
               c=color,
               edgecolors='none',
               s=size,
               label=adata.obs[key].cat.categories[imask],
               rasterized=settings._vector_friendly)
    return mask