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: config.rs
    path of file: ./repos/delta-rs/crates/azure/src
    
    the code of the file until where you have to start completion: //! Auxiliary module for generating a valig Azure configuration.
//!
//! Azure offers many different ways to authenticate against storage accounts and
//! provide credentials for a service principal. Some of this configutaion may
//! partially be specified in the environment. This module establishes a structured
//! way how we discover valid credential
    
    fn keys(&self) -> Vec<AzureConfigKey> {
        match self {
            Self::AccessKey => Vec::from_iter([AzureConfigKey::AccessKey]),
            Self::BearerToken => Vec::from_iter([AzureConfigKey::Token]),
            Self::ClientSecret => Vec::from_iter([
                AzureConfigKey::ClientId,
                AzureConfigKey::ClientSecret,
                AzureConfigKey::AuthorityId,
            ]),
            Self::WorkloadIdentity => Vec::from_iter([
                AzureConfigKey::AuthorityId,
                AzureConfigKey::ClientId,
                AzureConfigKey::FederatedTokenFile,
            ]),
            Self::SasKey => Vec::from_iter([AzureConfigKey::SasKey]),
            Self::ManagedIdentity => Vec::new(),
        }
    }