Methods to generate Metadata from DataFrames

[csala]

The Metadata class should be modified to assist on the creation of the metadata dictionary.

First, the metadata argument from the Metadata.__init__ method should be made optional (default to None).

Then, the following methods should be added:

• add_table(name, primary_key=None, fields=None, data=None, parent=None, foreign_key=None): a New table to the dataset.
  • all the arguments are optional.
  • If fields are given they can either be a list or dict. If they are a dict, they are validated and directly used.
  • If the data is given and fields are not, or they are given as a list, fields is built from the dataframe dtypes. If fields is a list, only those fields are used. Data can either be DataFrame or a path to a CSV file. If the path is relative, it must be relative to the Metadata root_path.
  • if a parent is given, a relationship is created using the foreign key of this table and the primary key of the parent. The parent must exist beforehand in the metadata.
  • Additional arguments such as anonymization details or regular expressions must set either inside the fields argument or afterwards.
• remove_table(table): remove the table from metadata. If child tables exist, relationships must be removed first.
• add_relationship(table, parent, foreign_key): Add an individual relationship between two tables. foreign_key field details are inherited from the parent table and validated against the table data.
• remove_relationship(table, parent): Remove the relationship between two tables.
• add_field(table, field, field_details): add a new field to the table. If the field already exists, an exception suggesting to use update_field is raised.
• update_field(table, field, field_deatils): replace the field specification with the given values.
• remove_field(table, field): remove a field from the table.
• to_dict(): Return the complete metadata specification as a dictionary.
• to_json(): Store the dict specification of the metadata in the given location. Use indent=4.