How to use the wand.api.library.MagickRelinquishMemory function in Wand

def safe_copy(ptr):
    """Safely cast memory address to char pointer, convert to python string,
    and immediately free resources.

    :param ptr: The memory address to convert to text string.
    :type ptr: :class:`ctypes.c_void_p`
    :returns: :class:`tuple` (:class:`ctypes.c_void_p`, :class:`str`)

    .. versionadded:: 0.5.3
    """
    string = ''
    if bool(ptr):
        string = ctypes.cast(ptr, ctypes.c_char_p).value
        ptr = library.MagickRelinquishMemory(ptr)
    return ptr, text(string)

def __iter__(self):
        image = self.image
        num = ctypes.c_size_t()
        props_p = library.MagickGetImageProperties(image.wand, b'', num)
        props = [text(props_p[i]) for i in xrange(num.value)]
        library.MagickRelinquishMemory(props_p)
        return iter(props)

def __del__(self):
        """Relinquishes memory allocated by ImageMagick.
        We don't need to worry about checking for ``NULL`` because
        :c:func:`MagickRelinquishMemory` does that for us.
        Note alslo that :class:`ctypes.c_char_p` has no
        :meth:`~object.__del__` method, so we don't need to
        (and indeed can't) call the superclass destructor.

        """
        try:
            from wand.api import library  # Lazy load global library
            library.MagickRelinquishMemory(self)
        except ImportError:
            # Python my be shutting down; and such, ``sys.meta_path``
            # may not be available.
            pass

.. versionadded:: 0.4.0

        .. versionchanged: 0.4.1
           Safely release allocated memory with
           :c:func:`MagickRelinquishMemory` instead of :c:func:`libc.free`.

        """
        number_elements = ctypes.c_size_t(0)
        dash_array_p = library.DrawGetStrokeDashArray(
            self.resource, ctypes.byref(number_elements)
        )
        dash_array = []
        if dash_array_p is not None:
            dash_array = [float(dash_array_p[i])
                          for i in xrange(number_elements.value)]
            library.MagickRelinquishMemory(dash_array_p)
        return dash_array

"""
        if format is not None:
            with self.convert(format) as converted:
                return converted.make_blob()
        library.MagickResetIterator(self.wand)
        length = ctypes.c_size_t()
        blob_p = None
        if len(self.sequence) > 1:
            blob_p = library.MagickGetImagesBlob(self.wand,
                                                 ctypes.byref(length))
        else:
            blob_p = library.MagickGetImageBlob(self.wand,
                                                ctypes.byref(length))
        if blob_p and length.value:
            blob = ctypes.string_at(blob_p, length.value)
            library.MagickRelinquishMemory(blob_p)
            return blob
        self.raise_exception()

def _repr_png_(self):  # pragma: no cover
        library.MagickResetIterator(self.image.wand)
        repr_wand = library.MagickAppendImages(self.image.wand, 1)
        length = ctypes.c_size_t()
        blob_p = library.MagickGetImagesBlob(repr_wand,
                                             ctypes.byref(length))
        if blob_p and length.value:
            blob = ctypes.string_at(blob_p, length.value)
            library.MagickRelinquishMemory(blob_p)
            return blob
        else:
            return None

def __len__(self):
        image = self.image
        num = ctypes.c_size_t()
        props_p = library.MagickGetImageProperties(image.wand, b'', num)
        library.MagickRelinquishMemory(props_p)
        return num.value

font_metrics_f = library.MagickQueryFontMetrics
        if isinstance(text, text_type):
            if self.text_encoding:
                text = text.encode(self.text_encoding)
            else:
                text = binary(text)
        result = font_metrics_f(image.wand, self.resource, text)
        if not result:  # pragma: no cover
            # Error on drawing context
            self.raise_exception()
            # Or error on image canvas
            image.raise_exception()
            # Generate a generic error if ImageMagick couldn't emit one.
            raise ValueError('Unable to render text with current font.')
        args = [result[i] for i in xrange(13)]
        library.MagickRelinquishMemory(result)
        return FontMetrics(*args)