toString method
A string representation of this object.
Some classes have a default textual representation,
often paired with a static parse function (like int.parse).
These classes will provide the textual representation as
their string representation.
Other classes have no meaningful textual representation
that a program will care about.
Such classes will typically override toString to provide
useful information when inspecting the object,
mainly for debugging or logging.
Implementation
@override
String toString() => 'PnL[expense=$expense, from=$from, income=$income, netIncome=$netIncome, to=$to, totalExpense=$totalExpense, totalIncome=$totalIncome]';