Hi,

This issue may be with the data type being passed as an argument in the SQL query.
Try this,

def _compute_timesheet_hour(self):
    for val in self:
        self._cr.execute('''SELECT project_id, employee_id, SUM(unit_amount) FROM         account_analytic_line
        WHERE project_id = %s AND employee_id = %s
        GROUP BY project_id, employee_id''', (val.project_id.id, val.employee_id.id,))
        res = self._cr.fetchone()
        if res and res[2]:
            val.timesheet_hour = res[2]
        else:
            val.timesheet_hour = 0.0

The SQL query passes a tuple of parameters (val.project_id.id, val.employee_id.id,) using placeholders of the form '%s'. This should help resolve the issue you're facing with adapting the argument types correctly

Regards