code: public Signature getSignatureBySigner(String email, String name) {
          if (email == null || name == null) {
              return null;
          }
          for (Signature s : getSignatures()) {
              if (name.equalsIgnoreCase(s.getName()) && email.equalsIgnoreCase(s.getEmail())) {
                  return s;
              }
          }
          return null;
      }
docs: Utility method that allows you to search for a Signature object on this
  request by email and name. It requires both because neither alone is
  enough to guarantee uniqueness (some requests can have multiple signers
  using the same email address or name).
  
  @param email String
  @param name String
  @return Signature, if found on this request, or null
  @deprecated Use getSignature(email, name)