Function frame_support::storage::migration::take_storage_item

pub fn take_storage_item<K: Encode + Sized, T: Decode + Sized, H: StorageHasher>(
    module: &[u8], 
    item: &[u8], 
    key: K
) -> Option<T>

Get a particular value in storage by the module, the map's item name and the key hash.