when implementing a button with ipywidgets the way to add a tooltip is:

import ipywidgets as wd
mybtn = wd.Button(description='load',
                       disabled=False,
                       button_style='', # 'success', 'info', 'warning', 'danger' or ''
                       tooltip='this will happen:... this will happen:...this will happen:...this will happen:...this will happen:...this will happen:...this will happen:...this will happen:...this will happen:...',
                       icon='',
                       layout=layout_btn)
mybtn.style.button_color = '#90ee90' # or 'lightgreen' or 'rgb(144,238,144)'
mybtn

that results in:

How can I make the tooltip font bigger?