Type    : Constructor
 Title   : new
 Usage   : my $mediator = Bio::Phylo::Taxa::TaxaMediator->new;
 Function: Instantiates a Bio::Phylo::Taxa::TaxaMediator
           object.
 Returns : A Bio::Phylo::Taxa::TaxaMediator object (singleton).
 Args    : None.
    

 Type    : Method
 Title   : register
 Usage   : $mediator->register( $obj );
 Function: Stores an object in mediator's cache, if relevant
 Returns : $self
 Args    : An object, $obj
 Comments: This method is called every time an object is instantiated.
    

 Type    : Method
 Title   : unregister
 Usage   : $mediator->unregister( $obj );
 Function: Cleans up mediator's cache of $obj and $obj's relations
 Returns : $self
 Args    : An object, $obj
 Comments: This method is called every time an object is destroyed.
    

 Type    : Method
 Title   : set_link
 Usage   : $mediator->set_link( -one => $obj1, -many => $obj2 );
 Function: Creates link between objects
 Returns : $self
 Args    : -one  => $obj1 (source of a one-to-many relationship)
           -many => $obj2 (target of a one-to-many relationship)
 Comments: This method is called from within, for example, set_taxa
           method calls. A call like $taxa->set_matrix( $matrix ),
           and likewise a call like $matrix->set_taxa( $taxa ), are 
           both internally rerouted to:

           $mediator->set_link( 
                -one  => $taxa, 
                -many => $matrix 
           );
    

 Type    : Method
 Title   : get_link
 Usage   : $mediator->get_link( 
               -source => $obj, 
               -type   => _CONSTANT_,
           );
 Function: Retrieves link between objects
 Returns : Linked object
 Args    : -source => $obj (required, the source of the link)
           -type   => a constant from Bio::Phylo::Util::CONSTANT

           (-type is optional, used to filter returned results in 
           one-to-many query).

 Comments: This method is called from within, for example, get_taxa
           method calls. A call like $matrix->get_taxa()
           and likewise a call like $forest->get_taxa(), are 
           both internally rerouted to:

           $mediator->get_link( 
               -source => $self # e.g. $matrix or $forest           
           );

           A call like $taxa->get_matrices() is rerouted to:

           $mediator->get_link( -source => $taxa, -type => _MATRIX_ );
    

 Type    : Method
 Title   : remove_link
 Usage   : $mediator->remove_link( -one => $obj1, -many => $obj2 );
 Function: Removes link between objects
 Returns : $self
 Args    : -one  => $obj1 (source of a one-to-many relationship)
           -many => $obj2 (target of a one-to-many relationship)

           (-many argument is optional)

 Comments: This method is called from within, for example, 
           unset_taxa method calls. A call like $matrix->unset_taxa() 
           is rerouted to:

           $mediator->remove_link( -many => $matrix );

           A call like $taxa->unset_matrix( $matrix ); is rerouted to:

           $mediator->remove_link( -one => $taxa, -many => $matrix );