var:read_data does not read other model

hi again.
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I have 1 read_data function with 3 model. that models names are case, applicant, party (I wrote here in English). I have a table view and I defined {var:read_data} in data provider. Columns list is:
case.case_id:ID
case.case_no:Case No
applicant.aplicant_name:Applicant
party.name:Party
​
"applicant.aplicant_name:Applicant" and "party.name:Party" column shown empty.
​

[read_data] => Array

is reading all of model. But
​
​

[var] => Array
                (
                    [0] => Array
                        (
                            [case] => Array
                                (

is reading only model of case. It does not read other 2 model.
​
Why and how can I solve it?
​
thank you