code: def cdf(self, x):
      return self.expect(upper=x)
  
imports: import numpy
  from scipy import special
  from statsmodels.sandbox.distributions.multivariate import mvstdtprob
  from .extras import mvnormcdf
label_desc: Use image node_id 5 for calling the BivariateNormal obj's underlying member method code with example usage: obj.cdf(x) and returns: self