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Using `Collection`s (and other types which rely on equality) to contain elements
with undefined equality is error-prone. For example, `Collection` itself does
not have well-defined equality: the `List` and `Set` subinterfaces are not
necessarily comparable.
```java
ImmutableList<Collection<Integer>> collectionsOfIntegers =
ImmutableList.of(ImmutableSet.of(1, 2), ImmutableSet.of(3, 4));
collectionsOfIntegers.contains(ImmutableSet.of(1, 2)); // true
collectionsOfIntegers.contains(ImmutableList.of(1, 2)); // false
```
```java
boolean containsTest(Collection<CharSequence>> charSequences) {
// True if `charSequences` actually contains Strings, but otherwise not necessarily.
return charSequences.contains("test");
}
```
In this case, an appropriate fix may be,
```java
boolean containsTest(Collection<CharSequence>> charSequences) {
// True if `charSequences` actually contains Strings, but otherwise not necessarily.
return charSequences.stream().anyMatch("test"::contentEquals);
}
```
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