FieldExtractor.getMetadataName() values of "name"
and "weight" (case-sensitive) are special. In particular, "name" is used throughout the
environment to uniquely identify Examples within a
Dataset. "weight" should only
be used for the
FieldExtractor supplied to
weightExtractor which is used by the system to weight
ClassDescriptionExtracts the field value and converts it to a double.Extracts the field value and converts it to a float.Extracts the field value and emits it as a String.An Extractor with special casing for loading the index from a Row.Extracts the field value and converts it to a int.Extracts a value from a single field to be placed in an
Example's metadata field.