docstr: checks if all affines are equal across frames
docstr_tok: ["checks","if","all","affines","are","equal","across","frames"]
code: def _check_affines(self):
      """checks if all affines are equal across frames"""
      nframes = self.get_nframes()
      if nframes == 1:
          return True
      affs = [self.get_frame_affine(i) for i in range(nframes)]
      if affs:
          i = iter(affs)
          first = next(i)
          for item in i:
              if not np.allclose(first, item):
                  return False
      return True
  
imports: import warnings
  from numbers import Integral
  import numpy
  from .arraywriters import make_array_writer
  from .fileslice import canonical_slicers, predict_shape, slice2outax
  from .spatialimages import SpatialHeader, SpatialImage
  from .volumeutils import array_from_file, make_dt_codes, native_code, swapped_code
  from .wrapstruct import WrapStruct
label_desc: Use image node_id 4 for calling the EcatSubHeader obj's underlying member method code with example usage: obj._check_affines() and returns: True, True, False