account-financial-reporting/mis_builder_analytic_cash_flow/models/mis_cash_flow_forecast_line.py

from odoo import fields, models, api, _
from odoo.exceptions import ValidationError


class MisCashFlowForecastLine(models.Model):

    _inherit = 'mis.cash_flow.forecast_line'

    analytic_account_id = fields.Many2one(
        comodel_name='account.analytic.account',
        string='Analytic Account',
        required=True,
        help='The account of the forecast line is only for informative '
        'purpose',
    )