Turtle and Observer Command

sum-of-frogs-with `[condition]
[list of commands]`

Reports the total value of `[list of commands]` when run over the
turtles of breed `frogs` that satisfy `condition`. If there are no `frogs` in which `condition` is true, 0 is
returned. Note: This command can
also be executed by patches, for example within an `ask-patches` statement.

Note: When a turtle calls the command, it is not included as part of the calculation.

Examples:
`sum-of-frogs-with [color = green] [age]` returns the sum of all
of the ages of the green `frogs`.

Related commands:
sum-of-frogs