I found the solution in  odoo models.py in the write method description

""" write(vals)

Updates all records in the current set with the provided values.

:param dict vals: fields to update and the value to set on them e.g::

        {'foo': 1, 'bar': "Qux"}

    will set the field ``foo`` to ``1`` and the field ``bar`` to
    ``"Qux"`` if those are valid (otherwise it will trigger an error).

:raise AccessError: * if user has no write rights on the requested object
                    * if user tries to bypass access rules for write on the requested object
:raise ValidateError: if user tries to enter invalid value for a field that is not in selection
:raise UserError: if a loop would be created in a hierarchy of objects a result of the operation (such as setting an object as its own parent)

* For numeric fields (:class:`~odoo.fields.Integer`,
  :class:`~odoo.fields.Float`) the value should be of the
  corresponding type
* For :class:`~odoo.fields.Boolean`, the value should be a
  :class:`python:bool`
* For :class:`~odoo.fields.Selection`, the value should match the
  selection values (generally :class:`python:str`, sometimes
  :class:`python:int`)
* For :class:`~odoo.fields.Many2one`, the value should be the
  database identifier of the record to set
* Other non-relational fields use a string for value

  .. danger::

      for historical and compatibility reasons,
      :class:`~odoo.fields.Date` and
      :class:`~odoo.fields.Datetime` fields use strings as values
      (written and read) rather than :class:`~python:datetime.date` or
      :class:`~python:datetime.datetime`. These date strings are
      UTC-only and formatted according to
      :const:`odoo.tools.misc.DEFAULT_SERVER_DATE_FORMAT` and
      :const:`odoo.tools.misc.DEFAULT_SERVER_DATETIME_FORMAT`
* .. _openerp/models/relationals/format:

  :class:`~odoo.fields.One2many` and
  :class:`~odoo.fields.Many2many` use a special "commands" format to
  manipulate the set of records stored in/associated with the field.

  This format is a list of triplets executed sequentially, where each
  triplet is a command to execute on the set of records. Not all
  commands apply in all situations. Possible commands are:

  ``(0, _, values)``
      adds a new record created from the provided ``value`` dict.
  ``(1, id, values)``
      updates an existing record of id ``id`` with the values in
      ``values``. Can not be used in :meth:`~.create`.
  ``(2, id, _)``
      removes the record of id ``id`` from the set, then deletes it
      (from the database). Can not be used in :meth:`~.create`.
  ``(3, id, _)``
      removes the record of id ``id`` from the set, but does not
      delete it. Can not be used on
      :class:`~odoo.fields.One2many`. Can not be used in
      :meth:`~.create`.
  ``(4, id, _)``
      adds an existing record of id ``id`` to the set. Can not be
      used on :class:`~odoo.fields.One2many`.
  ``(5, _, _)``
      removes all records from the set, equivalent to using the
      command ``3`` on every record explicitly. Can not be used on
      :class:`~odoo.fields.One2many`. Can not be used in
      :meth:`~.create`.
  ``(6, _, ids)``
      replaces all existing records in the set by the ``ids`` list,
      equivalent to using the command ``5`` followed by a command
      ``4`` for each ``id`` in ``ids``.

  .. note:: Values marked as ``_`` in the list above are ignored and
            can be anything, generally ``0`` or ``False``.
"""

i have field with one2many relation and it was enough to write self.my_one2Many_field = fields_lines