<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def load_from_file(self, fname=None):
 """Update rcParams from user-defined settings This function updates the instance with what is found in `fname` Parameters fname: str Path to the yaml configuration file. Possible keys of the dictionary are defined by :data:`config.rcsetup.defaultParams`. If None, the :func:`config.rcsetup.psyplot_fname` function is used. See Also -------- dump_to_file, psyplot_fname"""

        fname = fname or psyplot_fname()
        if fname and os.path.exists(fname):
            with open(fname) as f:
                d = yaml.load(f)
                self.update(d)
                if (d.get('project.plotters.user') and
                        'project.plotters' in self):
                    self['project.plotters'].update(d['project.plotters.user'])