```ruby
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

class Solr::Importer::Mapper
  def initialize(mapping)
    @mapping = mapping
  end
  
  def field_data(orig_data, field_name)
    orig_data[field_name]
  end
  
  def mapped_field_value(orig_data, field_mapping)
    case field_mapping
      when String
        field_mapping
      when Proc
        field_mapping.call(orig_data)
      when Symbol
        field_data(orig_data, field_mapping)
      when Enumerable
        field_mapping.collect {|orig_field_name| mapped_field_value(orig_data, orig_field_name)}.flatten
      else
        raise "Unknown mapping for #{field_mapping}"
    end
  end
  
  def map(orig_data)
    mapped_data = {}
    @mapping.each do |solr_name, field_mapping|
      value = mapped_field_value(orig_data, field_mapping)
      mapped_data[solr_name] = value if value
    end
    
    mapped_data
  end
  
  
  
  
end
```

Add option to stringify symbols when looking them up from an original object. An alternate approach could be to have two different classes, one for objects with symbol keys, and one for string keys
user
```ruby
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License.  You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

class Solr::Importer::Mapper
  def initialize(mapping, options={})
    @mapping = mapping
    @options = options
  end
  
  def field_data(orig_data, field_name)
    orig_data[field_name]
  end
  
  def mapped_field_value(orig_data, field_mapping)
    case field_mapping
      when String
        field_mapping
      when Proc
        field_mapping.call(orig_data)
      when Symbol
        field_data(orig_data, @options[:stringify_symbols] ? field_mapping.to_s : field_mapping)
      when Enumerable
        field_mapping.collect {|orig_field_name| mapped_field_value(orig_data, orig_field_name)}.flatten
      else
        raise "Unknown mapping for #{field_mapping}"
    end
  end
  
  def map(orig_data)
    mapped_data = {}
    @mapping.each do |solr_name, field_mapping|
      value = mapped_field_value(orig_data, field_mapping)
      mapped_data[solr_name] = value if value
    end
    
    mapped_data
  end
  
  
  
  
end
```
assistant