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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _normalize_group_attrs(self, attrs):
 """Normalize the attributes used to set groups If it's a list of one element, it just become this element. It raises an error if the attribute doesn't exist or if it's multivaluated. """

        for key in self.group_attrs_keys:
            if key not in attrs:
                raise MissingGroupAttr(key)
            if type(attrs[key]) is list and len(attrs[key]) == 1:
                attrs[key] = attrs[key][0]
            if type(attrs[key]) is list and len(attrs[key]) != 1:
                raise MultivaluedGroupAttr(key)