Pygmt.config

Hi, I am using pygmt 0.9. But whenever I am trying to use any parameters from pygmt.config it is showing too many warnings. Why it is happening?

import pygmt
fig = pygmt.Figure()
pygmt.config(FONT = ‘18p’)

and it showing these many warnings and error as well.

gmt [WARNING]: Length o not supported - revert to default unit [point]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Representation of font size not recognised. Using default.
gmt [ERROR]: Unrecognized keyword FONT_SUBTITLE.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [ERROR]: MAP_FRAME_AXES given illegal value (auto)!
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [ERROR]: MAP_FRAME_WIDTH given illegal value (autc)!
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
gmt [WARNING]: Length o not supported - revert to default unit [cm]
gmt [WARNING]: aut not a valid number and may not be decoded properly.
3 GMT Defaults conversion errors in file /home/lalit/.gmt/sessions/gmt_session.393563/gmt.conf.2!

And it is printing output like this:

[3]: pygmt.src.config.config at 0x7fc53c24be80>