presto-main/src/main/java/io/prestosql/sql/planner/LookupSymbolResolver.java/LookupSymbolResolver/LookupSymbolResolver
class LookupSymbolResolver:    public LookupSymbolResolver(Map<Symbol, ColumnHandle> assignments, Map<ColumnHandle, NullableValue> bindings)
    {
        requireNonNull(assignments, "assignments is null");
        requireNonNull(bindings, "bindings is null");

        this.assignments = ImmutableMap.copyOf(assignments);
        this.bindings = ImmutableMap.copyOf(bindings);
    }