def add(self, element, multiplicity=1):
        """Adds an element to the multiset.

        >>> ms = Multiset()
        >>> ms.add('a')
        >>> sorted(ms)
        ['a']

        An optional multiplicity can be specified to define how many of the element are added:

        >>> ms.add('b', 2)
        >>> sorted(ms)
        ['a', 'b', 'b']

        This extends the :meth:`MutableSet.add` signature to allow specifying the multiplicity.

        Args:
            element:
                The element to add to the multiset.
            multiplicity:
                The multiplicity i.e. count of elements to add.
        """
        if multiplicity < 1:
            raise ValueError("Multiplicity must be positive")
        self._elements[element] += multiplicity
        self._total += multiplicity
Adds an element to the multiset.

        >>> ms = Multiset()
        >>> ms.add('a')
        >>> sorted(ms)
        ['a']

        An optional multiplicity can be specified to define how many of the element are added:

        >>> ms.add('b', 2)
        >>> sorted(ms)
        ['a', 'b', 'b']

        This extends the :meth:`MutableSet.add` signature to allow specifying the multiplicity.

        Args:
            element:
                The element to add to the multiset.
            multiplicity:
                The multiplicity i.e. count of elements to add.