presto-spi/src/main/java/io/prestosql/spi/connector/ProjectionApplicationResult.java/ProjectionApplicationResult/Assignment
class ProjectionApplicationResult:        public Assignment(String variable, ColumnHandle column, Type type)
        {
            this.variable = requireNonNull(variable, "variable is null");
            this.column = requireNonNull(column, "column is null");
            this.type = requireNonNull(type, "type is null");
        }