title: B (billions) instead of G (giga) in python plotly customdata [SI prefix d3]
body: <p>I have gone through <a href="https://community.plotly.com/t/custom-si-unit-prefixes/29739" rel="nofollow noreferrer">this</a>, <a href="https://stackoverflow.com/questions/40774677/d3-formatting-tick-value-to-show-b-billion-instead-of-g-giga">this</a> and some other similar posts. They all give the solution in javascript which I am unable to port to python. Help would be appreciated.</p>
  <p>When I pass a value to <code>customdata</code> which is big enough to be a billion, it shows the sign as G (for giga) rather than B, whereas plotly defaults to B, the comparison can be seen in the image. Is there a way to use B instead of G?</p>
  <p><a href="https://i.stack.imgur.com/7UyaP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7UyaP.png" alt="enter image description here" /></a></p>
  <pre><code>import pandas as pd
  import plotly.express as px
  
  df = pd.DataFrame({'x':[500,3000,50000,100000,7000000,80000000,400000000,9000000000]})
  more_data = [100,3000,50000,600000,2000000,90000000,500000000,3000000000]
  
  fig = px.line(df, log_y=True)
  fig.update_traces(mode='lines+markers',
                    customdata=more_data,
                    hovertemplate='%{y}&lt;br&gt;%{customdata:,.1s}')
  </code></pre>