docstr: Get the help string for a single trait.
  
  If `inst` is given, it's current trait values will be used in place of
  the class default.
docstr_tok: ["Get","the","help","string","for","a","single","trait",".","If","`","inst","`","is","given",",","it","'s","current","trait","values","will","be","used","in","place","of","the","class","default","."]
code: def class_get_trait_help(cls, trait, inst=None):
      """Get the help string for a single trait.
  
      If `inst` is given, it's current trait values will be used in place of
      the class default.
      """
      assert inst is None or isinstance(inst, cls)
      lines = []
      header = "--%s.%s=<%s>" % (
          cls.__name__,
          trait.name,
          trait.__class__.__name__,
      )
      lines.append(header)
      if inst is not None:
          lines.append(
              indent("Current: %r" % getattr(inst, trait.name), 4)
          )
      else:
          try:
              dvr = trait.default_value_repr()
          except Exception:
              dvr = None  # ignore defaults we can't construct
          if dvr is not None:
              if len(dvr) > 64:
                  dvr = dvr[:61] + "..."
              lines.append(indent("Default: %s" % dvr, 4))
      if "Enum" in trait.__class__.__name__:
          # include Enum choices
          lines.append(indent("Choices: %r" % (trait.values,)))
  
      help = trait.help
      if help != "":
          help = "\n".join(wrap_paragraphs(help, 76))
          lines.append(indent(help, 4))
      return "\n".join(lines)
  
imports: from __future__ import print_function, absolute_import
  from copy import deepcopy
  import warnings
  from .loader import Config, LazyConfigValue, _is_section_key
  from traitlets.traitlets import HasTraits, Instance, observe, observe_compat, default
  from ipython_genutils.text import indent, dedent, wrap_paragraphs
label_desc: Use image node_id 8 for calling the Configurable obj's underlying member method code with example usage: obj.class_get_trait_help(cls, trait, inst) and returns: str