You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: unfold.rs
    path of file: ./repos/icu4x/components/casemap/src/provider
    
    the code of the file until where you have to start completion: // This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

//! Data for reverse folding

#[cfg(feature = "datagen")]
use alloc::string::String;
use icu_provider::prelude::*;
use zerovec::ule::UnvalidatedStr;
use zerovec::ZeroMap;

/// Reverse case folding data. Maps from multi-character strings back
/// to code-points that fold to those strings.
///
/// <div class="stab unstable">
/// ðŸš§ This code is considered unstable; it may change at any time, in breaking or non-breaking ways,
/// including in SemVer minor releases. While the serde representation of data structs is guaranteed
/// to be stable, their Rust representation might not be. Use with caution.
/// </div>
#[icu_provider::data_struct(marker(CaseMapUnfoldV1Marker, "props/casemap_unfold@1", singleton))]
#[cfg_attr(feature = "serde", derive(serde::Deserialize))]
#[cfg_attr(
    feature = "datagen",
    derive(serde::Serialize, databake::Bake),
    databake(path = icu_casemap::provider),
)]
#[derive(Debug, PartialEq, C
    
    pub fn try_from_icu(raw: &[u16]) -> Result<Self, DataError> {
        const ROWS_INDEX: usize = 0;
        const ROW_WIDTH_INDEX: usize = 1;
        const STRING_WIDTH_INDEX: usize = 2;

        if raw.len() <= STRING_WIDTH_INDEX {
            return Err(DataError::custom("Unfold: header missing"));
        }

        let num_rows = raw[ROWS_INDEX] as usize;
        let row_width = raw[ROW_WIDTH_INDEX] as usize;
        let string_width = raw[STRING_WIDTH_INDEX] as usize;

        if row_width == 0 {
            return Err(DataError::custom("Unfold: invalid row width"));
        }

        // Header takes up one row.
        let row_data = &raw[row_width..];

        let mut map = ZeroMap::new();

        debug_assert!(num_rows == row_data.chunks_exact(row_width).count());
        for row in row_data.chunks_exact(row_width) {
            let key = Self::decode_string(&row[..string_width])
                .ok_or(DataError::custom("Unfold: unpaired surrogate in key"))?;
            let val = Self::decode_string(&row[string_width..])
                .ok_or(DataError::custom("Unfold: unpaired surrogate in value"))?;
            if map
                .try_append(UnvalidatedStr::from_str(&key), val.as_ref())
                .is_some()
            {
                return Err(DataError::custom("Unfold: keys not sorted/unique"));
            }
        }
        Ok(Self { map })
    }