def font(row, col, sheet = nil)
      key = normalize(row, col)
      definition_index = safe_send(sheet_for(sheet).cells[key], :style)
      styles.definitions[definition_index] if definition_index
    end
def font(row, col, sheet = nil)
      key = normalize(row, col)
      definition_index = safe_send(sheet_for(sheet).cells[key], :style)
      styles.definitions[definition_index] if definition_index
    end
Given a cell, return the cell's style