def setChild(self, which, t):
"""Overrides Traversable's setChild to
enforce the rule that a child of an Expression must be
type Expression"""
if isinstance(t, Expression):
Traversable.setChild(self, which, t)
else:
raise ChildNotAnExpressionError(str(type(t)))
return self
def setChild(self, which, t):
"""Overrides the Traversable setChild to catch
unsupported child nodes"""
self._catchChildNotCorrectType(t)
Traversable.setChild(self, which, t)