public int getSignatureIndex() {
		return signatureIndex & 0xffff;
	}
The value of the signature_index item must be a valid index into the
constant_pool table. The constant pool entry at that index must be a
CONSTANT_Utf8_info structure representing either a class signature,
if this signature attribute is an attribute of a ClassFile structure, a method type
signature, if this signature is an attribute of a method_info structure, or a field
type signature otherwise.
@return a valid index into the constant_pool table
Ghidra/Processors/JVM/src/main/java/ghidra/javaclass/format/attributes/SignatureAttribute.java