def set_float_format(formatter):
global FLOAT_FORMATTER<EOL>FLOAT_FORMATTER = formatter<EOL>
Set the conversion format used to represent float distances and support
values in the newick representation of trees.

For example, use set_float_format('%0.32f') to specify 32 decimal numbers
when exporting node distances and bootstrap values.

Scientific notation (%e) or any other custom format is allowed. The
formatter string should not contain any character that may break newick
structure (i.e.: ":;,()")