The levels represent the minimum level range (level_1) and the maximum level range (level_2). For example, if you have a variable that has a minimum value of 0 and a maximum value of 100. You can use the default setting by setting level_1 = 1e20 and level_2 = 1e20. If you want to set the values by hand you can for example set level_1 = 20 (for the minimum value) and level_2 = 80 for the maximum value.
You can also set the specific levels by levels = (0, 20, 35, 40, 75, 100)
a.levels=(0,20,35,40,75,100) # Set the custom ranges
Let me know if this isn't clear.
From: Aashish Chaudhary <firstname.lastname@example.org:email@example.com>
what is level 1 and level 2 means? Is this the elevation?