async def get_users_with_roles(role_service, role):
    """Get mapping of group role grants on DB users.

    Args:
        role_service: A RoleService class instance.
        role: Name of IAM group role.

    Returns: List of all users who have the role granted to them.
    """
    role_grants = []
    grants = await role_service.fetch_role_grants(role)
    # loop through grants that are in tuple form (FROM_USER, TO_USER)
    for grant in grants:
        # add users who have role
        role_grants.append(grant[1])
    return role_grants