presto-main/src/main/java/io/prestosql/sql/analyzer/StatementAnalyzer.java/StatementAnalyzer/analyzeFrom
class StatementAnalyzer:        private Scope analyzeFrom(QuerySpecification node, Optional<Scope> scope)
        {
            if (node.getFrom().isPresent()) {
                return process(node.getFrom().get(), scope);
            }

            return createScope(scope);
        }