'Constructor
@param options: the options for the SELECT, as list of tuples
[(value, label)], or as dict {value: label},
or None to auto-detect the options from the
Field when called
@param cols: number of columns for the options table
@param help_field: field in the referenced table to retrieve
a tooltip text from (for foreign keys only)
@param none: True to render "None" as normal option
@param sort: sort the options'

def __init__(self, options=None, cols=None, help_field=None, none=None, sort=True):

    self.options = options
    self.cols = (cols or 3)
    self.help_field = help_field
    self.none = none
    self.sort = sort
