New in version 2.0.
True when expr is a sequence and expr meets the criteria for a restricted growth function:
abjad> from abjad.tools import sequencetools
abjad> sequencetools.is_restricted_growth_function([1, 1, 1, 1])
True
abjad> sequencetools.is_restricted_growth_function([1, 1, 1, 2])
True
abjad> sequencetools.is_restricted_growth_function([1, 1, 2, 1])
True
abjad> sequencetools.is_restricted_growth_function([1, 1, 2, 2])
True
Otherwise false:
abjad> sequencetools.is_restricted_growth_function([1, 1, 1, 3])
False
abjad> sequencetools.is_restricted_growth_function(17)
False
A restricted growth function is a sequence l such that l[0] == 1 and such that l[i] <= max(l[:i]) + 1 for 1 <= i <= len(l).
Return boolean.