class_docstr: Labelled arrow for use as a quiver plot scale key.
class_docstr_tok: ["Labelled","arrow","for","use","as","a","quiver","plot","scale","key","."]
code: def __init__(self, Q, X, Y, U, label, **kw):
      martist.Artist.__init__(self)
      self.Q = Q
      self.X = X
      self.Y = Y
      self.U = U
      self.angle = kw.pop("angle", 0)
      self.coord = kw.pop("coordinates", "axes")
      self.color = kw.pop("color", None)
      self.label = label
      self._labelsep_inches = kw.pop("labelsep", 0.1)
      self.labelsep = self._labelsep_inches * Q.ax.figure.dpi
  
      # try to prevent closure over the real self
      weak_self = weakref.ref(self)
  
      def on_dpi_change(fig):
          self_weakref = weak_self()
          if self_weakref is not None:
              self_weakref.labelsep = (
                  self_weakref._labelsep_inches * fig.dpi
              )
              self_weakref._initialized = (
                  False  # simple brute force update
              )
              # works because _init is
              # called at the start of
              # draw.
  
      self._cid = Q.ax.figure.callbacks.connect(
          "dpi_changed", on_dpi_change
      )
  
      self.labelpos = kw.pop("labelpos", "N")
      self.labelcolor = kw.pop("labelcolor", None)
      self.fontproperties = kw.pop("fontproperties", dict())
      self.kw = kw
      _fp = self.fontproperties
      # boxprops = dict(facecolor='red')
      self.text = mtext.Text(
          text=label,  # bbox=boxprops,
          horizontalalignment=self.halign[self.labelpos],
          verticalalignment=self.valign[self.labelpos],
          fontproperties=font_manager.FontProperties(**_fp),
      )
  
      if self.labelcolor is not None:
          self.text.set_color(self.labelcolor)
      self._initialized = False
      self.zorder = Q.zorder + 0.1
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  import math
  import weakref
  import numpy
  from numpy import ma
  import matplotlib.collections
  import matplotlib.transforms
  import matplotlib.text
  import matplotlib.artist
  from matplotlib.artist import allow_rasterization
  from matplotlib import docstring
  import matplotlib.font_manager
  from matplotlib.cbook import delete_masked_points
  from matplotlib.patches import CirclePolygon
label_desc: Use image node_id 1 to create a new QuiverKey object from inherited base classes: martist with example: obj = QuiverKey(Q, X, Y, U, label)