def _get_region(self, buffer, start, count):
        '''Map a buffer region using this attribute as an accessor.

        The returned region can be modified as if the buffer was a contiguous
        array of this attribute (though it may actually be interleaved or
        otherwise non-contiguous).

        The returned region consists of a contiguous array of component
        data elements.  For example, if this attribute uses 3 floats per
        vertex, and the `count` parameter is 4, the number of floats mapped
        will be ``3 * 4 = 12``.

        :Parameters:
            `buffer` : `AbstractMappable`
                The buffer to map.
            `start` : int
                Offset of the first vertex to map.
            `count` : int
                Number of vertices to map

        :rtype: `AbstractBufferRegion`
        '''
        byte_start = self.stride * start
        byte_size = self.stride * count
        array_count = self.count * count
        if self.stride == self.size or not array_count:
            # non-interleaved
            ptr_type = ctypes.POINTER(self.c_type * array_count)
            return buffer.get_region(byte_start, byte_size, ptr_type)
        else:
            # interleaved
            byte_start += self.offset
            byte_size -= self.offset
            elem_stride = self.stride // ctypes.sizeof(self.c_type)
            elem_offset = self.offset // ctypes.sizeof(self.c_type)
            ptr_type = ctypes.POINTER(
                self.c_type * int((count * elem_stride - elem_offset)))
            region = buffer.get_region(byte_start, byte_size, ptr_type)
            return vertexbuffer.IndirectArrayRegion(
                region, array_count, self.count, elem_stride)
Map a buffer region using this attribute as an accessor.

        The returned region can be modified as if the buffer was a contiguous
        array of this attribute (though it may actually be interleaved or
        otherwise non-contiguous).

        The returned region consists of a contiguous array of component
        data elements.  For example, if this attribute uses 3 floats per
        vertex, and the `count` parameter is 4, the number of floats mapped
        will be ``3 * 4 = 12``.

        :Parameters:
            `buffer` : `AbstractMappable`
                The buffer to map.
            `start` : int
                Offset of the first vertex to map.
            `count` : int
                Number of vertices to map

        :rtype: `AbstractBufferRegion`