code: public Map<String, Object> checkExistence(String argument, Setup setup) {
          this.requestMaker = new RequestMaker(setup);
          String argumentType;
  
          if (isTaxDocument(argument)) argumentType = "tax_document";
  
          else argumentType = "email";
  
          RequestProperties props = new RequestPropertiesBuilder()
                  .method("GET")
                  .endpoint(String.format("%s/exists?%s=%s", ENDPOINT, argumentType, argument))
                  .type(Accounts.class)
                  .contentType(CONTENT_TYPE)
                  .build();
  
          return this.requestMaker.doRequest(props);
      }
docs: This method allows you to check if a person already has a Moip account, by it's tax document or e-mail.
  The tax document must be write with punctuation, for example: 123.456.789-00.
  
  @param   argument
  {@code String} the person's tax document or e-mail.
  
  @param   setup
  {@code Setup} the setup object.
  
  @return  {@code Map<String, Object>}