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Walker was the son of David Walker , the abolitionist , who wrote an appeal calling for the end of slavery in 1829 .
 person: Walker; person: David Walker
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Walker, David Walker 
Answer:
 person: Walker; person: David Walker