How to robustly simplify an object (including a number)

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Hi,

When writing a package, I met the following problem:

Say, I want the variable 'a' to be an expression, which is passed to the package by user. Then I want to call a.simplify() to simplify the expression.

However, as an input, a could naturally be the following cases:

# case 1
a = var('t')
# case 2
a = 1
# case 3
a = 0.1

a.simplify() will work on 1, but not work on 2 or 3, which crashes the whole package.

I could do something as

try:
    b = a.simplify()
except:
    b = a

But this really seems like a workaround instead of something formal. Is there a better way to handle this case? Thanks!