title: openerp inherit from report_account_common
body: <p>I'm creating a jasper report for balance sheet and I saw that the following file:
  "addons\account\report\account_financial_report.py" has a method that gets all information needed for my report, so I want to create a module that can get that method (get_lines) and can generate my new report from that values.</p>
  
  <p>Is it possible? that file has the following:</p>
  
  <pre><code>class report_account_common(report_sxw.rml_parse, common_report_header):
      def __init__(self, cr, uid, name, context=None):
          super(report_account_common, self).__init__(cr, uid, name, context=context)
          self.localcontext.update( {
              'get_lines': self.get_lines,
              'time': time,
              'get_fiscalyear': self._get_fiscalyear,
              'get_account': self._get_account,
              'get_start_period': self.get_start_period,
              'get_end_period': self.get_end_period,
              'get_filter': self._get_filter,
              'get_start_date':self._get_start_date,
              'get_end_date':self._get_end_date,
              'get_target_move': self._get_target_move,
          })
          self.context = context
  
      def set_context(self, objects, data, ids, report_type=None):
          new_ids = ids
          if (data['model'] == 'ir.ui.menu'):
              new_ids = 'chart_account_id' in data['form'] and [data['form']['chart_account_id']] or []
              objects = self.pool.get('account.account').browse(self.cr, self.uid, new_ids)
          return super(report_account_common, self).set_context(objects, data, new_ids, report_type=report_type)
  
      def get_lines(self, data):
          lines = []
          account_obj = self.pool.get('account.account')
           ..... more code ...... 
  </code></pre>
  
  <p>So I want to call to get_lines method and work with the value returned.</p>
  
  <p>Thanks in advance.</p>