def __strict(self):
def conc(a, b):<EOL><INDENT>return a + b<EOL><DEDENT>b = np.array(reduce(conc, [[i.top.z, i.base.z] for i in self]))<EOL>return all(np.diff(b) >= <NUM_LIT:0>)<EOL>
Private method. Checks if striplog is monotonically increasing in
depth.

Returns:
    Bool.