code: def _merge_asized(base, other, level=0):
      
      ref2key = lambda ref: ref.name.split(':')[0]
      base.size += other.size
      base.flat += other.flat
      if level > 0:
          base.name = ref2key(base)
      # Add refs from other to base. Any new refs are appended.
      base.refs = list(base.refs) # we may need to append items
      refs = {}
      for ref in base.refs:
          refs[ref2key(ref)] = ref
      for ref in other.refs:
          key = ref2key(ref)
          if key in refs:
              _merge_asized(refs[key], ref, level=level+1)
          else:
              # Don't modify existing Asized instances => deepcopy
              base.refs.append(deepcopy(ref))
              base.refs[-1].name = key
docs: Merge **Asized** instances `base` and `other` into `base`.