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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def user_create(username,
                user=None,
                host=None,
                port=None,
                maintenance_db=None,
                password=None,
                createdb=None,
                createroles=None,
                inherit=None,
                login=None,
                connlimit=None,
                encrypted=None,
                superuser=None,
                replication=None,
                rolepassword=None,
                valid_until=None,
                groups=None,
                runas=None):
    '''
    Creates a Postgres user.

    CLI Examples:

    .. code-block:: bash

        salt '*' postgres.user_create 'username' user='user' \\
                host='hostname' port='port' password='password' \\
                rolepassword='rolepassword' valid_until='valid_until'
    '''
    return _role_create(username,
                        typ_='user',
                        user=user,
                        host=host,
                        port=port,
                        maintenance_db=maintenance_db,
                        password=password,
                        createdb=createdb,
                        createroles=createroles,
                        inherit=inherit,
                        login=login,
                        connlimit=connlimit,
                        encrypted=encrypted,
                        superuser=superuser,
                        replication=replication,
                        rolepassword=rolepassword,
                        valid_until=valid_until,
                        groups=groups,
                        runas=runas)