anchor.diff:  every characteristics
   must be followed by a Term Source REF and Term Accession Number. Details on both are
   the next items in this table | Organism is a mandatory attribute in BioSamples,
  -so *Characteristics[Organism]* is mandatory
  +so *Characteristics[Organism]* is mandatory | Valid value for *Characteristics[Organism]* is mandatory
   
  -|Term Source REF | Identifies the controlled vocabulary that this term comes from. Examples are NCBITAXON, BTO
  +|Term Source REF | Identifies the controlled vocabulary that this term comes from.
  +Examples are NCBITAXON, BTO
  +| Mandatory
   | Optional
   
   |Term Accession Number | The accession number from the Source (Term Source Ref), example for
   Organism = Homo Sapiens and Term Source Ref = NCBITAXON, the Term Accession Number is
   http://purl.obolibrary.org/obo/NCBITaxon_9606
  +| Mandatory
   | Optional
   
   |Comment[bsd_relationship:<relationship_type>] | The sample relationship with any other
  
positive.code: 
  == Example output file
  
  [%header,format=tsv]
  |===
  include::files/isa-result-example.tsv[]
  |===
  
negative.code: name in the file. If you wish to establish a relationship with a sample that is already in BioSamples
  you need to mention the accession of the sample
  | Optional
  | Optional
  
  |Comment[external DB REF] | The reference to this sample in any other database
  | Optional
  | Optional
  
  |Comment[submission_contact:email] | The email address of the submitter
  | Optional
  | Optional
  
  |Sample Identifier | The ID/ accession of the sample. In case of new sample submission it
  is optional, mandatory if you are looking to update existing samples
  | Optional (for new submissions)
  / mandatory (for sample updates)
  | Optional (for new submissions)
  / mandatory (for sample updates)
  |===
  
  == Example file
  
  [width="100%" %header,format=tsv]
  |===
  include::files/isa-example.tsv[]
  |===
  