class_docstr: XY Line graph class
docstr: All y values
code: def yvals(self):
      """All y values"""
      return [
          val[1]
          for serie in self.series
          for val in serie.values
          if val[1] is not None
      ]
  
file_path: pygal/pygal/graph/xy.py
imports: from functools import reduce
  from pygal.graph.dual import Dual
  from pygal.graph.line import Line
  from pygal.util import cached_property, compose, ident
label_desc: Use image node_id 2 for calling the XY obj's underlying member method code with example usage: obj.yvals() and returns: unknown