presto-main/src/main/java/io/prestosql/sql/analyzer/StatementAnalyzer.java/StatementAnalyzer/getFunctionMetadata
class StatementAnalyzer:        private FunctionMetadata getFunctionMetadata(FunctionCall functionCall)
        {
            ResolvedFunction resolvedFunction = analysis.getResolvedFunction(functionCall);
            verify(resolvedFunction != null, "function has not been analyzed yet: %s", functionCall);
            return metadata.getFunctionMetadata(resolvedFunction);
        }