class_docstr: Context for fast low-precision arithmetic (53-bit precision, giving at most
  about 15-digit accuracy), using Python's builtin float and complex.
code: def sum_accurately(ctx, terms, check_step=1):
      s = ctx.zero
      k = 0
      for term in terms():
          s += term
          if (not k % check_step) and term:
              if abs(term) <= 1e-18 * abs(s):
                  break
          k += 1
      return s
  
imports: from .ctx_base import StandardBaseContext
  import math
  import cmath
  from .None import math2
  from .None import function_docs
  from .libmp import mpf_bernoulli, to_float, int_types
  from .None import libmp
label_desc: Use image node_id 29 for calling the FPContext obj's underlying member method code with example usage: obj.sum_accurately(ctx, terms, check_step) and returns: s