docstr: Return the cap height as float.
code: def get_capheight(self):
      """Return the cap height as float."""
      return self._header[b"CapHeight"]
  
imports: from collections import namedtuple
  import logging
  import re
  from ._mathtext_data import uni2type1
label_desc: Use image node_id 19 for calling the AFM obj's underlying member method code with example usage: obj.get_capheight() and returns: self