question: @ Nullable private Operator . Kind parseOperator ( TokenStream tokens ) { if ( tokens . has ( "=" ) ) { tokens . next ( ) ; tokens . expect ( "=" ) ; return Operator . Kind . EQUALS ; } if ( tokens . has ( "!" ) ) { tokens . next ( ) ; tokens . expect ( "=" ) ; return Operator . Kind . NOT_EQUALS ; } if ( tokens . has ( "<" ) ) { tokens . next ( ) ; if ( tokens . has ( "=" ) ) { tokens . next ( ) ; return Operator . Kind . LESS_EQUAL ; } return Operator . Kind . LESS ; } if ( tokens . has ( ">" ) ) { tokens . next ( ) ; if ( tokens . has ( "=" ) ) { tokens . next ( ) ; return Operator . Kind . GREATER_EQUAL ; } return Operator . Kind . GREATER ; } return null ; }
target:  Check for and get an operator kind.