code: def serialize(cls, obj, buf, lineLength, validate=True):
          
  
          cls.generateImplicitParameters(obj)
          if validate:
              cls.validate(obj, raiseException=True)
          if obj.isNative:
              transformed = obj.transformFromNative()
              undoTransform = True
          else:
              transformed = obj
              undoTransform = False
          out = None
          outbuf = buf or six.StringIO()
          if obj.group is None:
              groupString = ''
          else:
              groupString = obj.group + '.'
          if obj.useBegin:
              foldOneLine(outbuf, "{0}BEGIN:{1}".format(groupString, obj.name),
                          lineLength)
  
          try:
              first_props = [s for s in cls.sortFirst if s in obj.contents \
                                      and not isinstance(obj.contents[s][0], Component)]
              first_components = [s for s in cls.sortFirst if s in obj.contents \
                                      and isinstance(obj.contents[s][0], Component)]
          except Exception:
              first_props = first_components = []
              # first_components = []
  
          prop_keys = sorted(list(k for k in obj.contents.keys() if k not in first_props \
                                           and not isinstance(obj.contents[k][0], Component)))
          comp_keys = sorted(list(k for k in obj.contents.keys() if k not in first_components \
                                          and isinstance(obj.contents[k][0], Component)))
  
          sorted_keys = first_props + prop_keys + first_components + comp_keys
          children = [o for k in sorted_keys for o in obj.contents[k]]
  
          for child in children:
              # validate is recursive, we only need to validate once
              child.serialize(outbuf, lineLength, validate=False)
          if obj.useBegin:
              foldOneLine(outbuf, "{0}END:{1}".format(groupString, obj.name),
                          lineLength)
          out = buf or outbuf.getvalue()
          if undoTransform:
              obj.transformToNative()
          return out
docs: Set implicit parameters, do encoding, return unicode string.
  
          If validate is True, raise VObjectError if the line doesn't validate
          after implicit parameters are generated.
  
          Default is to call base.defaultSerialize.