code: def _f_cdf(dfn, dfd, x):
      if x < 0:
          return mpmath.mpf(0)
      dfn, dfd, x = mpmath.mpf(dfn), mpmath.mpf(dfd), mpmath.mpf(x)
      ub = dfn * x / (dfn * x + dfd)
      res = mpmath.betainc(dfn / 2, dfd / 2, x2=ub, regularized=True)
      return res
  
imports: import itertools
  import numpy
  from numpy.testing import assert_equal, assert_allclose
  import pytest
  import scipy.special
  from scipy.special._testutils import MissingModule, check_version, FuncData
  from scipy.special._mptestutils import Arg, IntArg, get_args, mpf2float, assert_mpmath_equal
label_desc: Use image node_id 3 for calling a global function with example usage: _f_cdf(dfn, dfd, x) and returns: res, mpmath