code: def first_parameter(self, singular_value):
          
          self.log("calc first term parameter @" + str(singular_value))
          first_term = self.I_minus_R(singular_value) * self.parcov * \
                       self.I_minus_R(singular_value)
          self.log("calc first term parameter @" + str(singular_value))
          return first_term
docs: get the null space term (first term) contribution to parameter error variance
              at a singular value
  
          Parameters
          ----------
          singular_value : int
              singular value to calc first term at
  
          Returns
          -------
          first_term : pyemu.Cov
              first term contribution to parameter error variance