Function account_fetch_policy_for_source 

pub fn account_fetch_policy_for_source(
    source_chain_id: ChainId,
    network_profile: NetworkConfigs,
) -> AccountFetchPolicy

Returns the account-loading policy required by a fork source.

A recognized source chain ID is authoritative. The endpoint’s execution profile is only a source hint for custom chain IDs, where the chain ID cannot identify the RPC semantics.