'Place Df in the gradient of all functions.'

def place_Df(self, big_Df, Df, var_offsets, vert_offset):

    horiz_offset = 0
    for var in self.variables():
        var_size = (var.size[0] * var.size[1])
        var_Df = Df[:, horiz_offset:(horiz_offset + var_size)]
        self.block_add(big_Df, var_Df, vert_offset, var_offsets[var.data], (self.size[0] * self.size[1]), var_size)
        horiz_offset += var_size
