Function to extract geometry using the molecule's name from the PubChem

Used in the notebooks

Used in the tutorials

database. The 'structure' argument can be used to specify which structure info to use to extract the geometry. If structure=None, the geometry will be constructed based on 3D info, if available, otherwise on 2D (to keep backwards compatibility with the times when the argument 'structure' was not implemented).

name a string giving the molecule's name as required by the PubChem database.
structure a string '2d' or '3d', to specify a specific structure information to be retrieved from pubchem. The default is None. Recommended value is '3d'.

geometry a list of tuples giving the coordinates of each atom with distances in Angstrom.