docstr: Create and return a new GridlineCollection instance.
  
  *which* : "major" or "minor"
  *axis* : "both", "x" or "y"
docstr_tok: ["Create","and","return","a","new","GridlineCollection","instance",".","*","which","*",":","``","major","''","or","``","minor","''","*","axis","*",":","``","both","''",",","``","x","''","or","``","y","''"]
code: def new_gridlines(self, grid_helper=None):
      """
      Create and return a new GridlineCollection instance.
  
      *which* : "major" or "minor"
      *axis* : "both", "x" or "y"
  
      """
      if grid_helper is None:
          grid_helper = self.get_grid_helper()
  
      gridlines = grid_helper.new_gridlines(self)
  
      return gridlines
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import warnings
  import numpy
  from matplotlib import rcParams
  import matplotlib.artist
  import matplotlib.axes
  from matplotlib.path import Path
  from matplotlib.transforms import Bbox
  from .axisline_style import AxislineStyle
  from .axis_artist import AxisArtist, GridlinesCollection
label_desc: Use image node_id 6 for calling the Axes obj's underlying member method code with example usage: obj.new_gridlines(grid_helper) and returns: gridlines