init

We need to load Google's JS.

render

load_params

Load the ``packages'' required for the visualization; define a "packages_to_load" method which returns a list of them.

render_data

Renders the columns and the data.

add_columns

Adds the columns to the visualization. Each column is a key-value pair; the key is the column's "id" and the value is either a string (the "type") or a hashref. The hashref may specify "type" and "label". If no "label" is given, the "id" is used.

It will return a hashref of canonicalized columns.

add_data

Adds the data to the chart. Each data point should be a hash reference of column id to value.

encode_value