code: def find_in_coord_list_pbc(fcoord_list, fcoord, atol=1e-8):
      
      if len(fcoord_list) == 0:
          return []
      fcoords = np.tile(fcoord, (len(fcoord_list), 1))
      fdist = fcoord_list - fcoords
      fdist -= np.round(fdist)
      return np.where(np.all(np.abs(fdist) < atol, axis=1))[0]
docs: Get the indices of all points in a fractional coord list that are
      equal to a fractional coord (with a tolerance), taking into account
      periodic boundary conditions.
  
      Args:
          fcoord_list: List of fractional coords
          fcoord: A specific fractional coord to test.
          atol: Absolute tolerance. Defaults to 1e-8.
  
      Returns:
          Indices of matches, e.g., [0, 1, 2, 3]. Empty list if not found.