Note: ReferenceModel assumes t_end is a float, which implies it cannot be nothing

[haakon-e]

in get_profile, we allow for tf=nothing, which fetches the profile at the time ti. however, for practical purposes, ReferenceModel is used in conjunction with get_profile, which assumes that t_end is a Real number. As such, the special case of tf=nothing in get_profile is never reached.

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note: ti=t_start, tf=t_end