docs: def _initParams(self, init_method=None):
          """ this function initializes the paramenter and Ifilter """
          if self.bgRE:
              if init_method=='random':
                  params0 = {'covar': sp.randn(self._gpNull.covar.getNumberParams())}
              else:
                  if self.P==1:
                      params0 = {'covar':sp.sqrt(0.5) * sp.ones(2)}
                  else:
                      cov = 0.5*sp.cov(self.Y.T) + 1e-4*sp.eye(self.P)
                      chol = la.cholesky(cov, lower=True)
                      params = chol[sp.tril_indices(self.P)]
                      params0 = {'covar': sp.concatenate([params, params])}
          else:
              if self.P==1:
                  params_cn = sp.array([1.])
              else:
                  cov = sp.cov(self.Y.T) + 1e-4*sp.eye(self.P)
                  chol = la.cholesky(cov, lower=True)
                  params_cn = chol[sp.tril_indices(self.P)]
              params0 = {'covar': params_cn}
          return params0