docs: def getEstTraitCovar(self,term_i=None):
          """
          Returns explicitly the estimated trait covariance matrix
  
          Args:
              term_i:     index of the term we are interested in
          """
          assert self.P>1, 'Trait covars not defined for single trait analysis'
          
          if term_i==None:
              RV=SP.zeros((self.P,self.P))
              for term_i in range(self.n_terms): RV+=self.vd.getTerm(term_i).getTraitCovar().K()
          else:
              assert term_i<self.n_terms, 'Term index non valid'
              RV = self.vd.getTerm(term_i).getTraitCovar().K()
          return RV