Update fix_bond_react.txt

A map file has a header and a body. The header of map file the

contains one mandatory keyword and three optional keywords. The

mandatory keyword is 'equivalences' and the optional keywords are

'edgeIDs' and 'deleteIDs' and 'customIDs':

mandatory keyword is 'equivalences':

N {equivalences} = # of atoms N in the reaction molecule templates :pre

The optional keywords are 'edgeIDs', 'deleteIDs', 'customIDs' and

'constraints':

N {equivalences} = # of atoms N in the reaction molecule templates

N {edgeIDs} = # of edge atoms N in the pre-reacted molecule template

N {deleteIDs} = # of atoms N that are specified for deletion

N {customIDs} = # of atoms N that are specified for a custom update

# this is a map file :pre

2 edgeIDs

7 equivalences :pre

7 equivalences

2 edgeIDs :pre

BondingIDs :pre