How to use the datashader.utils.dynd_to_np_mask function in datashader

def dynd_op(op, left, right):
    if isinstance(left, nd.array):
        left_np, left_missing = dynd_to_np_mask(left)
        left_option = is_option(left.dtype)
    else:
        left_np, left_missing = left, False
        left_option = False
    if isinstance(right, nd.array):
        right_np, right_missing = dynd_to_np_mask(right)
        right_option = is_option(right.dtype)
    else:
        right_np, right_missing = right, False
        right_option = False
    out = op(left_np, right_np)
    if left_option or right_option:
        if out.dtype in dynd_missing_types:
            out[left_missing | right_missing] = dynd_missing_types[out.dtype]
            out = nd.asarray(out)
            return nd.asarray(out).view_scalars('?' + str(out.dtype))
        else:
            raise ValueError("Missing type unknown")
    return nd.asarray(out)

def f(self):
        arr, missing = dynd_to_np_mask(self._data)
        out = op(arr)
        if is_option(self._data.dtype):
            out[missing] = dynd_missing_types[out.dtype]
            out = nd.asarray(out).view_scalars('?' + str(out.dtype))
        else:
            out = nd.asarray(out)
        return ScalarAggregate(out, self.x_axis, self.y_axis)
    return f

def dynd_op(op, left, right):
    if isinstance(left, nd.array):
        left_np, left_missing = dynd_to_np_mask(left)
        left_option = is_option(left.dtype)
    else:
        left_np, left_missing = left, False
        left_option = False
    if isinstance(right, nd.array):
        right_np, right_missing = dynd_to_np_mask(right)
        right_option = is_option(right.dtype)
    else:
        right_np, right_missing = right, False
        right_option = False
    out = op(left_np, right_np)
    if left_option or right_option:
        if out.dtype in dynd_missing_types:
            out[left_missing | right_missing] = dynd_missing_types[out.dtype]
            out = nd.asarray(out)
            return nd.asarray(out).view_scalars('?' + str(out.dtype))

def _where_helper(agg, cond, otherwise):
    if not isboolean(cond.dshape):
        raise TypeError("cond must be a boolean aggregate")
    _validate_aligned(agg, cond)
    cond_arr, _ = dynd_to_np_mask(cond._data)
    arr, arr_mask = dynd_to_np_mask(agg._data)
    arr_missing = is_option(agg._data.dtype)
    while cond_arr.ndim < arr.ndim:
        cond_arr = np.expand_dims(cond_arr, -1)
    if isinstance(otherwise, Aggregate):
        _validate_aligned(agg, otherwise)
        otherwise_arr, otherwise_mask = dynd_to_np_mask(otherwise._data)
        while otherwise_arr.ndim < arr.ndim:
            otherwise_arr = np.expand_dims(otherwise_arr, -1)
            otherwise_mask = np.expand_dims(otherwise_mask, -1)
        otherwise_missing = is_option(otherwise._data.dtype)
    elif isinstance(otherwise, (int, float, np.generic)):
        otherwise_arr = otherwise
        otherwise_mask = otherwise_missing = False
    elif otherwise is None:
        otherwise_arr = dynd_missing_types[arr.dtype]

def _where_helper(agg, cond, otherwise):
    if not isboolean(cond.dshape):
        raise TypeError("cond must be a boolean aggregate")
    _validate_aligned(agg, cond)
    cond_arr, _ = dynd_to_np_mask(cond._data)
    arr, arr_mask = dynd_to_np_mask(agg._data)
    arr_missing = is_option(agg._data.dtype)
    while cond_arr.ndim < arr.ndim:
        cond_arr = np.expand_dims(cond_arr, -1)
    if isinstance(otherwise, Aggregate):
        _validate_aligned(agg, otherwise)
        otherwise_arr, otherwise_mask = dynd_to_np_mask(otherwise._data)
        while otherwise_arr.ndim < arr.ndim:
            otherwise_arr = np.expand_dims(otherwise_arr, -1)
            otherwise_mask = np.expand_dims(otherwise_mask, -1)
        otherwise_missing = is_option(otherwise._data.dtype)
    elif isinstance(otherwise, (int, float, np.generic)):
        otherwise_arr = otherwise
        otherwise_mask = otherwise_missing = False
    elif otherwise is None:
        otherwise_arr = dynd_missing_types[arr.dtype]
        otherwise_mask = False