def map(self, func):
    """
    A lazy way to apply the given function to each element in the stream.
    Useful for type casting, like:

    >>> from audiolazy import count
    >>> count().take(5)
    [0, 1, 2, 3, 4]
    >>> my_stream = count().map(float)
    >>> my_stream.take(5) # A float counter
    [0.0, 1.0, 2.0, 3.0, 4.0]

    """
    self._data = xmap(func, self._data)
    return self
A lazy way to apply the given function to each element in the stream.
    Useful for type casting, like:

    >>> from audiolazy import count
    >>> count().take(5)
    [0, 1, 2, 3, 4]
    >>> my_stream = count().map(float)
    >>> my_stream.take(5) # A float counter
    [0.0, 1.0, 2.0, 3.0, 4.0]