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, ax):
      """
      Create and return a new GridlineCollection instance.
  
      *which* : "major" or "minor"
      *axis* : "both", "x" or "y"
  
      """
      gridlines = GridlinesCollection(
          None,
          transform=ax.transData,
          colors=rcParams["grid.color"],
          linestyles=rcParams["grid.linestyle"],
          linewidths=rcParams["grid.linewidth"],
      )
      ax._set_artist_props(gridlines)
      gridlines.set_grid_helper(self)
  
      ax.axes._set_artist_props(gridlines)
      # gridlines.set_clip_path(self.axes.patch)
      # set_clip_path need to be deferred after Axes.cla is completed.
      # It is done inside the cla.
  
      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 7 for calling the GridHelperBase obj's underlying member method code with example usage: obj.new_gridlines(ax) and returns: gridlines