class_docstr: A Chart is an abstract baseclass for elements representing one or
  more independent and dependent variables defining a 1D coordinate
  system with associated values. The independent variables or key
  dimensions map onto the x-axis while the dependent variables are
  usually mapped to the location, height or spread along the
  y-axis. Any number of additional value dimensions may be
  associated with a Chart.
  
  If a chart's independent variable (or key dimension) is numeric
  the chart will represent a discretely sampled version of the
  underlying continuously sampled 1D space. Therefore indexing along
  this variable will automatically snap to the closest coordinate.
  
  Since a Chart is a subclass of a Dataset it supports the full set
  of data interfaces but usually each dimension of a chart represents
  a column stored in a dictionary, array or DataFrame.
code: def __getitem__(self, index):
      return super().__getitem__(index)
  
imports: import numpy
  import param
  from ..core import Dataset, Dimension, Element2D, NdOverlay, Overlay, util
  from ..core.dimension import process_dimensions
  from .geom import Points, Rectangles, VectorField
  from .selection import Selection1DExpr
label_desc: Use image node_id 2 for calling the Chart obj's underlying member method code with example usage: obj.__getitem__(index) and returns: super