import daft
from daft import col
df = daft.from_pydict({
    "nested_list": [[[0.1], [0.2]], [[0.3], [0.4]], [[0.5], [0.6]]]
})

inner_dtype = daft.DataType.fixed_size_list(daft.DataType.float64(), 1)
outer_dtype = daft.DataType.fixed_size_list(inner_dtype, 2)

(df
  .select(col("nested_list").cast(outer_dtype))
  .collect()
)