Removes all <values> from the values of <key>. If <key> has no
        remaining values after removevalues(), the key is popped.

        Example:
          omd = omdict([(1, 1), (1, 11), (1, 1), (1, 111)])
          omd.removevalues(1, [1, 111])
          omd.allitems() == [(1, 11)]

        Returns: <self>.

def removevalues(self, key, values):
        """
        Removes all <values> from the values of <key>. If <key> has no
        remaining values after removevalues(), the key is popped.

        Example:
          omd = omdict([(1, 1), (1, 11), (1, 1), (1, 111)])
          omd.removevalues(1, [1, 111])
          omd.allitems() == [(1, 11)]

        Returns: <self>.
        """
        self.setlist(key, [v for v in self.getlist(key) if v not in values])
        return self