presto-main/src/main/java/io/prestosql/operator/aggregation/AggregationMetadata.java/ParameterType/inputChannelParameterType
class ParameterType:            static ParameterType inputChannelParameterType(boolean isNullable, boolean isBlock, String methodName)
            {
                if (isBlock) {
                    if (isNullable) {
                        return NULLABLE_BLOCK_INPUT_CHANNEL;
                    }
                    else {
                        return BLOCK_INPUT_CHANNEL;
                    }
                }
                else {
                    if (isNullable) {
                        throw new IllegalArgumentException(methodName + " contains a parameter with @NullablePosition that is not @BlockPosition");
                    }
                    else {
                        return INPUT_CHANNEL;
                    }
                }
            }