def __init__(self, numticks = None, presets=None):
self.numticks = numticks<EOL>if presets is None:<EOL><INDENT>self.presets = {}<EOL><DEDENT>else:<EOL><INDENT>self.presets = presets<EOL><DEDENT>
Use presets to set locs based on lom.  A dict mapping vmin, vmax->locs