ExtensionArray.
isna
A 1-D array indicating if each value is missing.
In most cases, this should return a NumPy ndarray. For exceptional cases like SparseArray, where returning an ndarray would be expensive, an ExtensionArray may be returned.
SparseArray
Notes
If returning an ExtensionArray, then
na_values._is_boolean should be True
na_values._is_boolean
na_values should implement ExtensionArray._reduce()
ExtensionArray._reduce()
na_values.any and na_values.all should be implemented
na_values.any
na_values.all