mergeField method
Implementation
void mergeField(int number, UnknownFieldSetField field) {
_ensureWritable('mergeField');
_getField(number)
..varints.addAll(field.varints)
..fixed32s.addAll(field.fixed32s)
..fixed64s.addAll(field.fixed64s)
..lengthDelimited.addAll(field.lengthDelimited)
..groups.addAll(field.groups);
}