class_docstr: Button widget.
  
  This widget has an `on_click` method that allows you to listen for the
  user clicking on the button.  The click event itself is stateless.
  
  Parameters
  ----------
  description: str
     description displayed next to the button
  tooltip: str
     tooltip caption of the toggle button
  icon: str
     font-awesome icon name
  disabled: bool
     whether user interaction is enabled
class_docstr_tok: ["Button","widget",".","This","widget","has","an","`","on_click","`","method","that","allows","you","to","listen","for","the","user","clicking","on","the","button",".","The","click","event","itself","is","stateless",".","Parameters","--","--","--","--","--","description",":","str","description","displayed","next","to","the","button","tooltip",":","str","tooltip","caption","of","the","toggle","button","icon",":","str","font-awesome","icon","name","disabled",":","bool","whether","user","interaction","is","enabled"]
docstr: Strip 'fa-' if necessary'
docstr_tok: ["Strip","'fa-","'","if","necessary","'"]
code: def _validate_icon(self, proposal):
      """Strip 'fa-' if necessary'"""
      value = proposal["value"]
      if value.startswith("fa-"):
          warnings.warn(
              "icons names no longer start with 'fa-', "
              "just use the class name itself (for example, 'check' instead of 'fa-check')",
              DeprecationWarning,
          )
          value = value[3:]
      return value
  
file_path: catboost/contrib/python/ipywidgets/py2/ipywidgets/widgets/widget_button.py
imports: from .domwidget import DOMWidget
  from .widget import CallbackDispatcher, register, widget_serialization
  from .widget_core import CoreWidget
  from .widget_style import Style
  from .trait_types import Color, InstanceDict
  from traitlets import Unicode, Bool, CaselessStrEnum, Instance, validate, default
  import warnings
label_desc: Use image node_id 2 for calling the Button obj's underlying member method code with example usage: obj._validate_icon(proposal) and returns: value