def where_constraints
      @where.reduce({}) { |memo, constraint| memo[constraint.operation] = constraint.value; memo }
    end
def where_constraints
      @where.reduce({}) { |memo, constraint| memo[constraint.operation] = constraint.value; memo }
    end
Formats the current set of Parse::Constraint instances in the where clause
 as an expression hash.
 @return [Hash] the set of constraints