sub frequencies_form_a_sequence 
{
     my ($r) = @_;
     my $min = min keys %$r; 
     return 0 if $min == 1; # Just for test.
     my $max = max keys %$r; 
     return 0 if $min == $max; # Probably not a sequence.
     my $bool = all { defined $r->{$_} } $min .. $max;
}