sdk/src/com/socialize/google/gdata/util/common/base/Preconditions.java
public static <T extends Iterable<?>> T checkContentsNotNull(
      T iterable, Object errorMessage) {
    if (containsOrIsNull(iterable)) {
      throw new NullPointerException(String.valueOf(errorMessage));
    }
    return iterable;
  }
public static <T extends Iterable<?>> T checkContentsNotNull(
      T iterable, Object errorMessage) {
    if (containsOrIsNull(iterable)) {
      throw new NullPointerException(String.valueOf(errorMessage));
    }
    return iterable;
  }
Ensures that an {@code Iterable} object passed as a parameter to the
calling method is not null and contains no null elements.

@param iterable the iterable to check the contents of
@param errorMessage the exception message to use if the check fails; will
be converted to a string using {@link String#valueOf(Object)}
@return the non-null {@code iterable} reference just validated
@throws NullPointerException if {@code iterable} is null or contains at
least one null element