Defining a form to capture query parameters

Next, in /path/to/repo/www/chapter_09/trends/forms.py, we define a form class, TrendForm, which captures the query parameters used to formulate the revenue trends report. The fields that are defined here are ultimately used to form a query filter. The trend_region field could be used to include states, provinces, or even countries, such as England in the UK. The last field, trend_factor, is used for the purposes of future revenue projection. The initial value is .10, which represents revenue growth of 10%. The step attribute is .01, and represents the increment value for this number field.