def mask(self, m, indices=False):
return to_mask(self, m, indices=indices)<EOL>
obj.mask(m) yields the set of vertex labels from the given vertex-set object obj that
  correspond to the mask m.

The mask m may take any of the following forms:
   * a list of vertex indices
   * a boolean array (one value per vertex)
   * a property name, which can be cast to a boolean array
   * a tuple (property, value) where property is a list of values, one per vertex, and value
     is the value that must match in order for a vertex to be included (this is basically
     equivalent to the mask (property == value); note that property may also be a property
     name
   * a tuple (property, min, max), which specifies that the property must be between min and
     max for a vertex to be included (min < p <= max)
   * a tuple (property, (val1, val2...)), which specifies that the property must be any of
     the values in (val1, val2...) for a vertex to be included
   * None, indicating that all labels should be returned

Note that the optional argument indices (default: False) may be set to true to yield the
vertex indices instead of the vertex labels.