public String getHeader(String header) {
        if (headers == null) return null;

        return headers.get(header);
    }
Returns the value of the header with the specified name from the
response, or null if not present.

@param header
           The name of the header to lookup.

@return The value of the header with the specified name from the
        response, or null if not present.
aws-java-sdk-core/src/main/java/com/amazonaws/transform/StaxUnmarshallerContext.java