def __init__(self, required=True, default=None, field_name=None,<EOL>raw_field_name=None, mutable=True, read_only=False):
self.required = required<EOL>self.default = default<EOL>self.mutable = mutable<EOL>self.field_name = field_name<EOL>self.raw_field_name = raw_field_name or field_name<EOL>self.read_only = read_only<EOL>
By default, the field name is derived from the schema model, but in
certain cases it can be overridden. Specifying field_name overrides
both the name of the field in the raw (unclean) data, as well as in the
clean data model. If the raw data has a different field name than the
clean data, raw_field_name can be overridden.