'Set the list of fields to be used by the mapper.
The format of *fields* is::
[ (fieldName, {options}), ... ]
Field Options:
mode           Either \'range\' or \'enum\' (default is range). For \'range\',
The user may specify a gradient of colors to be applied
linearly across a specific range of values. For \'enum\',
the user specifies a single color for each unique value
(see *values* option).
units          String indicating the units of the data for this field.
values         List of unique values for which the user may assign a
color when mode==\'enum\'. Optionally may specify a dict
instead {value: name}.'

def setFields(self, fields):

    self.fields = OrderedDict(fields)
    names = self.fieldNames()
    self.setAddList(names)
