returns the result of interpretting the object as an instance of ` head ' . this implementation returns null ; returning a non-null result will terminate the switch . concode_field_sep PrimarykeyjoinPackage modelPackage concode_field_sep T doSwitch concode_elem_sep T doSwitch concode_elem_sep T doSwitch concode_elem_sep T defaultCase concode_elem_sep T caseBody
T function ( Head arg0 ) { return null ; }