code: def missing_inds(x, format_data=True):
      
  
      if format_data:
          x = formatter(x, ppca=False)
  
      inds = []
      for arr in x:
          if np.argwhere(np.isnan(arr)).size is 0:
              inds.append(None)
          else:
              inds.append(np.argwhere(np.isnan(arr))[:,0])
      if len(inds) > 1:
          return inds
      else:
          return inds[0]
docs: Returns indices of missing data
  
      This function is useful to identify rows of your array that contain missing
      data or nans.  The returned indices can be used to remove the rows with
      missing data, or label the missing data points that are interpolated
      using PPCA.
  
      Parameters
      ----------
      x : array or list of arrays
  
      format_data : bool
          Whether or not to first call the format_data function (default: True).
  
      Returns
      ----------
      inds : list, or list of lists
          A list of indices representing rows with missing data. If a list of
          numpy arrays is passed, a list of lists will be returned.