code: public static Constraint isHuman()
  	{
  		return new OR(
  			new MappedConst(new Field("SequenceEntityReference/organism/displayName",
  				Field.Operation.INTERSECT, "Homo sapiens"), 0),
  			new MappedConst(new Field("PhysicalEntity/entityReference/organism/displayName",
  				Field.Operation.INTERSECT, "Homo sapiens"), 0));
  	}
docs: Makes sure the EntityReference or the PhysicalEntity belongs to human. Please note that this
  check depends on the display name of the related BioSource object to be "Homo sapiens". If
  that is not the case, the constraint won't work.
  @return constraint to make sure the EntityReference or the PhysicalEntity belongs to human