Error when creating custom seaborn colormap

I'm trying to create my own colormap object for a seaborn heatmap.

But when I type in:

import seaborn as sns
new_map = sns.diverging_palette(220, 10, as_cmap=True)

I get the following error:

TypeError: 'float' object cannot be interpreted as an integer

What am I doing wrong?

Thanks in advance!