How to use function which is inside rust file

[GaloisField2718]

Hello everyone,

I have a question about policy.rs file (but it's a more general question).

We have :

pub enum RoleKind {
    /// Matches everyone, who is not matched by other roles.
    Everyone,
    /// Member greater or equal than given balance. Can use `1` as non-zero balance.
    Member(U128),
    /// Set of accounts.
    Group(HashSet<AccountId>),
}

Just after there is an implementation of RoleKind

impl RoleKind {
    /// Checks if user matches given role.
    pub fn match_user(&self, user: &UserInfo) -> bool {
        match self {
            RoleKind::Everyone => true,
            RoleKind::Member(amount) => user.amount >= amount.0,
            RoleKind::Group(accounts) => accounts.contains(&user.account_id),
        }
    }

    /// Returns the number of people in the this role or None if not supported role kind.
    pub fn get_role_size(&self) -> Option<usize> {
        match self {
            RoleKind::Group(accounts) => Some(accounts.len()),
            _ => None,
        }
    }

    pub fn add_member_to_group(&mut self, member_id: &AccountId) -> Result<(), ()> {
        match self {
            RoleKind::Group(accounts) => {
                accounts.insert(member_id.clone());
                Ok(())
            }
            _ => Err(()),
        }
    }

    pub fn remove_member_from_group(&mut self, member_id: &AccountId) -> Result<(), ()> {
        match self {
            RoleKind::Group(accounts) => {
                accounts.remove(member_id);
                Ok(())
            }
            _ => Err(()),
        }
    }
}

I want to use get_role_size but I don't know how to call it.