@VisibleForTesting
  boolean hasOneUdfMethod(UdfMetadata udfMetadata) {
    Class<?> udfClass = udfMetadata.getUdfMethod().getDeclaringClass();
    int numAnnotatedUdfMethods = 0;
    for (Method method : udfClass.getMethods()) {
      if (method.isAnnotationPresent(SamzaSqlUdfMethod.class)) {
        numAnnotatedUdfMethods += 1;
      }
    }
    return numAnnotatedUdfMethods == 1;
  }
Checks if there is only one UdfMethod in the input {@link UdfMetadata}.
@param udfMetadata the metadata for a UDF.
@return true if there is only one udf method defined in the UdfMetadata.
        false otherwise.
samza-sql/src/main/java/org/apache/samza/sql/planner/Checker.java