[yocto] ExpansionError during parsing

[Nemicolopterus Crypticus]

I can't seem to get simple bash code to parse properly in my recipes.
I have something like this:

do_install_prepend(){
     bb.build.exec_func('do_change_dir', d)
}

do_change_dir(){
     cd <a directory>
 }

I get this when I try bitbake -c clean -f <project>:
NOTE: Error during finalise of <path>/<to>/<recipe>/recipe.bb          |
ETA:  --:--:--
ERROR: ExpansionError during parsing <path>/<to>/<recipe>/recipe.bb:
Failure expanding variable do_install: ShellSyntaxError:
LexToken(TOKEN,"'do_change_dir',",0,0)
followed by:
  LexToken(TOKEN,'d',0,0)
  LexToken(RPARENS,')',0,0)
  LexToken(NEWLINE,'\n',0,0)
  LexToken(TOKEN,'autotools_do_install',0,0)
  LexToken(NEWLINE,'\n',0,0)

This looks identical to this:
https://www.mail-archive.com/yocto%40yoctoproject.org/msg09403.html
https://www.mail-archive.com/yocto%40yoctoproject.org/msg04862.html

What am I missing?
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