code: def cross_above(values1, values2, start=-2, end=None):
      """Checks for a cross above conditions over the specified period between two DataSeries objects.
  
      It returns the number of times values1 crossed above values2 during the given period.
  
      :param values1: The DataSeries that crosses.
      :type values1: :class:`pyalgotrade.dataseries.DataSeries`.
      :param values2: The DataSeries being crossed.
      :type values2: :class:`pyalgotrade.dataseries.DataSeries`.
      :param start: The start of the range.
      :type start: int.
      :param end: The end of the range.
      :type end: int.
  
      .. note::
          The default start and end values check for cross above conditions over the last 2 values.
      """
      return _cross_impl(values1, values2, start, end, lambda x: x > 0)
  
label_desc: Use image node_id 4 for calling a global function with example usage: cross_above(values1, values2, start, end) and returns: _cross_impl