code: def qbarfrom(ctx, q=None, m=None, k=None, tau=None, qbar=None):
      r"""
      Returns the number-theoretic nome `\bar q`, given any of
      `q, m, k, \tau, \bar{q}`::
  
          >>> from mpmath import *
          >>> mp.dps = 25; mp.pretty = True
          >>> qbarfrom(qbar=0.25)
          0.25
          >>> qbarfrom(q=qfrom(qbar=0.25))
          0.25
          >>> qbarfrom(m=extraprec(20)(mfrom)(qbar=0.25))  # ill-conditioned
          0.25
          >>> qbarfrom(k=extraprec(20)(kfrom)(qbar=0.25))  # ill-conditioned
          0.25
          >>> qbarfrom(tau=taufrom(qbar=0.25))
          (0.25 + 0.0j)
  
      """
      if qbar is not None:
          return ctx.convert(qbar)
      if q is not None:
          return ctx.convert(q) ** 2
      if m is not None:
          return nome(ctx, m) ** 2
      if k is not None:
          return nome(ctx, ctx.convert(k) ** 2) ** 2
      if tau is not None:
          return ctx.expjpi(2 * tau)
  
imports: from .functions import defun, defun_wrapped
label_desc: Use image node_id 4 for calling a global function with example usage: qbarfrom(ctx, q, m, k, tau, qbar) and returns: ctx, unknown, unknown, unknown, ctx