allow multiple calls to Validate
allow multiple calls to Validate

ShaperTools/openhtf,grybmadsci/openhtf,fahhem/openhtf,google/openhtf,grybmadsci/openhtf,jettisonjoe/openhtf,ShaperTools/openhtf,google/openhtf,fahhem/openhtf,amyxchen/openhtf,jettisonjoe/openhtf,google/openhtf,fahhem/openhtf,grybmadsci/openhtf,ShaperTools/openhtf,ShaperTools/openhtf,google/openhtf,fahhem/openhtf,ShaperTools/openhtf,grybmadsci/openhtf,amyxchen/openhtf,jettisonjoe/openhtf,jettisonjoe/openhtf