docs: def slice_yx(r, pval, ydim=1):
      """slice a correlation and p-value matrix of a (y,X) dataset
      into a (y,x_i) vector and (x_j, x_k) matrices
  
      Parameters
      ----------
      r : ndarray
          Correlation Matrix of a (y,X) dataset
  
      pval : ndarray
          p-values
  
      ydim : int
          Number of target variables y, i.e. the first ydim-th columns
          and rows are (y, x_i) correlations
  
      Returns
      -------
      y_r : ndarray
          1D vector or ydim-column array with (y,x) correlations
  
      y_pval : ndarray
          1D vector or ydim-column array with (y,x) p-values
  
      x_r : ndarray
          correlation matrix (x_j, x_k)
  
      x_pval : ndarar
          matrix with p-values
  
      Example
      -------
          import korr
          r, pval = korr.mcc(np.c_[y, X])
          y_r, y_pval, x_r, x_pval = slice_yx(r, pval, ydim=1)
          print(np.c_[y_r, y_pval])
          korr.corrgram(x_r, x_pval)
      """
      if ydim is 1:
          return (
              r[1:, :1].reshape(-1, ), pval[1:, :1].reshape(-1, ),
              r[1:, 1:], pval[1:, 1:])
      else:
          return (
              r[ydim:, :ydim], pval[ydim:, :ydim],
              r[ydim:, ydim:], pval[ydim:, ydim:])