code: def read_transform(fid):
      """Read 64bit float matrix transform from bti file."""
      return read_double_matrix(fid, rows=4, cols=4)
  
imports: import numpy
  from ..._fiff.utils import read_str
label_desc: Use image node_id 18 for calling a global function with example usage: read_transform(fid) and returns: read_double_matrix