A Colour It Never Saw

A paint shop's model has a colour column. Training taught it some colours. Later, a customer asks about a colour it has never seen, and that must not crash anything.

Task: write encode_colours(train_colours, new_colours).

• Put each list in a one-column DataFrame whose column is named "colour".
• Fit a OneHotEncoder(handle_unknown="ignore") on the training colours.
• Transform the new colours with it. An unseen colour comes out as all zeroes.
• Return a dict:
  • "columns": the encoder's output column names, from get_feature_names_out(), as a list of strings.
  • "rows": the encoded new colours as a list of lists of whole numbers (0 or 1), one inner list per new colour.