code: def _convert_tol(ctx, tol):
      if isinstance(tol, int_types):
          return from_int(tol)
      if isinstance(tol, float):
          return from_float(tol)
      if hasattr(tol, "_mpf_"):
          return tol._mpf_
      prec, rounding = ctx._prec_rounding
      if isinstance(tol, str):
          return from_str(tol, prec, rounding)
      raise ValueError("expected a real number, got %s" % tol)
  
imports: from sympy.external.gmpy import MPQ
  from sympy.polys.domains.domainelement import DomainElement
  from sympy.utilities import public
  from mpmath.ctx_mp_python import PythonMPContext, _mpf, _mpc, _constant
  from mpmath.libmp import MPZ_ONE, fzero, fone, finf, fninf, fnan, round_nearest, mpf_mul, repr_dps, int_types, from_int, from_float, from_str, to_rational
label_desc: Use image node_id 4 for calling the MPContext obj's underlying member method code with example usage: obj._convert_tol(ctx, tol) and returns: from_int, from_float, tol, from_str