code: def is_bash_builtin(cmd):
    
    # from compgen -b
    bash_builtins = ['alias', 'bg', 'bind', 'alias', 'bg', 'bind', 'break',
                     'builtin', 'caller', 'cd', 'command', 'compgen', 'complete',
                     'compopt', 'continue', 'declare', 'dirs', 'disown', 'echo',
                     'enable', 'eval', 'exec', 'exit', 'export', 'false', 'fc',
                     'fg', 'getopts', 'hash', 'help', 'history', 'jobs', 'kill',
                     'let', 'local', 'logout', 'mapfile', 'popd', 'printf',
                     'pushd', 'pwd', 'read', 'readarray', 'readonly', 'return',
                     'set', 'shift', 'shopt', 'source', 'suspend', 'test',
                     'times', 'trap', 'true', 'type', 'typeset', 'ulimit',
                     'umask', 'unalias', 'unset', 'wait']
    toks = cmd.split()
    if toks and toks[0] in bash_builtins:
      return True
    return False
docs: Return true if command is invoking bash built-in