- Usage:
`n = countGraphs(L, s)``n = countGraphs(L, h)``n = countGraphs(L, l)`

- Inputs:
`L`, a list, containing graphs (mixed formats are allowed)`s`, a string, a filter, as generated by buildGraphFilter`h`, a hash table, a filter, as used by buildGraphFilter`l`, a list, a filter, as used by buildGraphFilter

- Outputs:
`n`, an integer, the number of graphs in*L*satisfying the filter

Counts the number of graphs in a list that satisfy certain restraints as given in the filter (see buildGraphFilter). Notice that the input list can be graphs represented as instances of the class Graph or in a nauty-based String format.

For example, we can count the number of connected graphs on five vertices.

i1 : L = generateGraphs 5; |

i2 : countGraphs(L, {"Connectivity" => 0, "NegateConnectivity" => true}) o2 = 21 |

- buildGraphFilter -- creates the appropriate filter string for use with filterGraphs and countGraphs
- filterGraphs -- filters (i.e., selects) graphs in a list for given properties

- countGraphs(List,HashTable)
- countGraphs(List,List)
- countGraphs(List,String)