code: @Override
      public ProposalPersonContract getPrincipalInvestigator(ProposalDevelopmentDocumentContract pdDoc) {
          ProposalPersonContract proposalPerson = null;
          if (pdDoc != null) {
              for (ProposalPersonContract person : pdDoc.getDevelopmentProposal().getProposalPersons()) {
                  if (person.isPrincipalInvestigator()) {
                      proposalPerson = person;
                  }
              }
          }
          return proposalPerson;
      }
docs: This method is to get PrincipalInvestigator from person list
  
  @param pdDoc Proposal development document.
  @return ProposalPerson PrincipalInvestigator for the proposal.