code: def read_tag(fid, pos, shape=None, rlims=None):
      """Read a Tag from a file at a given position.
  
      Parameters
      ----------
      fid : file
          The open FIF file descriptor.
      pos : int
          The position of the Tag in the file.
      shape : tuple | None
          If tuple, the shape of the stored matrix. Only to be used with
          data stored as a vector (not implemented for matrices yet).
      rlims : tuple | None
          If tuple, the first (inclusive) and last (exclusive) rows to retrieve.
          Note that data are assumed to be stored row-major in the file. Only to
          be used with data stored as a vector (not implemented for matrices
          yet).
  
      Returns
      -------
      tag : Tag
          The Tag read.
      """
      tag = _read_tag_header(fid, pos)
      if tag is None:
          return tag
      if tag.size > 0:
          if _matrix_info(tag) is not None:
              tag.data = _read_matrix(fid, tag, shape, rlims)
          else:
              #   All other data types
              try:
                  fun = _call_dict[tag.type]
              except KeyError:
                  raise Exception(
                      f"Unimplemented tag data type {tag.type}"
                  ) from None
              tag.data = fun(fid, tag, shape, rlims)
      return tag
  
imports: import html
  import re
  import struct
  from dataclasses import dataclass
  from functools import partial
  from typing import Any
  import numpy
  from scipy.sparse import csc_matrix, csr_matrix
  from ..utils import _check_option, warn
  from ..utils.numerics import _julian_to_cal
  from .constants import FIFF, _ch_coil_type_named, _ch_kind_named, _ch_unit_mul_named, _ch_unit_named, _dig_cardinal_named, _dig_kind_named
label_desc: Use image node_id 19 for calling a global function with example usage: read_tag(fid, pos, shape, rlims) and returns: tag, tag